Name: the preparation and properties of thermo-reversibly cross-linked rubber via diels-alder chemistry
Uploaded: 2016-08-25T15:00:00.000+00:00
Duration: 7 min 2 s
Description: Watch this Scientific Journal Video about The Preparation and Properties of Thermo-reversibly Cross-linked Rubber Via Diels-Alder Chemistry at JoVE.com

This research forms part of the research program of the Dutch Polymer Institute, project #749.

1. Gomma modifica <ol><li> Preparare la EPM maleated (EPM-g-MA, 49% in peso di etilene, 2,1% in peso MA, Mn = 50 kg / mol, PDI = 2.0) in gomma e furfurylamine (FFA) prima di iniziare l&#39;esperimento, come indicato nei passaggi 1.1.1 1.1.4. 5 <ol><li> Essiccare la gomma EPM-g-MA in stufa sotto vuoto per un&#39;ora a 175 ° C per convertire presente di-acido in anidride. 11 </li><li> stampo a compressione dello 0,1 mm film gomma spessa in una pressa a caldo per 10 min a 150 ° C e 100 bar. </li><li> Registrare un spettro infrarosso trasmissione della pellicola risultante dopo il suo inserimento in un supporto tablet KBr. NOTA: La conversione del idrolizzato di-acido in anidride è completa se il tipico picco dell&#39;acido carbossilico ( <img alt="Equazione" src="/files/ftp_upload/54496/54496eq_v-sCO.jpg" /> = 1.710 centimetri -1) è assente e la caratteristica di picco anidride ciclica ( <img alt="Equazione" src="/files/ftp_upload/54496/54496eq_v-asCO.jpg" /> = 1.856 cm -1 </sup&gt;) è presente. 5 </li><li> Utilizzando vetreria distillazione standard distillare 2,8 g FFA (punto di ebollizione = 145 ° C, 28,9 mmol; 3,0 eq base al contenuto MA in EPM-g-MA.) A pressione atmosferica. </li></ol></li><li> Preparare una soluzione di gomma 10 wt% pesando 45,0 g di gomma EPM-g-MA (9.6 mmol MA) e sciogliendolo in 500 ml di tetraidrofurano (THF) a 23 ° C in un contenitore chiuso sotto vigorosa agitazione. </li><li> Aggiungere 2,8 g distillata di fresco FFA alla soluzione di gomma 10% in peso. </li><li> Mescolare la miscela di reazione in un sistema chiuso a 23 ° C per almeno 1 ora. </li><li> Precipitare la miscela di reazione versandolo lentamente in un dieci volte (5 L) di acetone sotto agitazione meccanica, ottiene il prodotto polimerico come fili bianchi che sono facilmente ripescato del becher usando pinzette grande. </li><li> Essiccare il prodotto raccolto (EPM-g-furano) fino a peso costante in un forno sotto vuoto a 35 ° C (questo richiede circa 1 giorno). </li><li> Compressione muffa la risultante, slightly prodotto giallastro in uno stampo tra due piastre di metallo in una pressa a caldo per 10 min a 175 ° C e 100 bar per convertire il prodotto intermedio acido maleammico nel prodotto immide. </li><li> Tagliare la placca risultante della gomma in piccoli pezzi (0,05 g) con le forbici e lavarle accuratamente immergendole in acetone per rimuovere ogni FFA non ha reagito. </li><li> Registrare una trasmissione spettro infrarosso del prodotto in un supporto tablet KBr dopo stampaggio a compressione in film spesso ± 0,1 mm. 5 NOTA: L&#39;assenza di qualsiasi residuo ammide-acido può dedurre dall&#39;assenza di un picco a 1530 cm -1 39, 40 L&#39;indicazione più illustrativa per la modifica riuscita sono la scomparsa quasi completa. <img alt="Equazione" src="/files/ftp_upload/54496/54496eq_v-asCO.jpg" /> a 1856 cm-1 dell&#39;anidride e la comparsa di <img alt="Equazione" src="/files/ftp_upload/54496/54496eq_v-sCO.jpg" /> a 1.710 cm -1e il CN stiramento vibrazioni ( <img alt="Equazione" src="/files/ftp_upload/54496/54496eq_v-sCN.jpg" /> = 1378 centimetri -1) della maleimide. </li><li> Determinare la conversione reazione di EPM-g-MA per EPM-g-furano dalla diminuzione di assorbanza del C = O vibrazione simmetrica tratto di gruppi di anidride ( <img alt="Equazione" src="/files/ftp_upload/54496/54496eq_v-asCO.jpg" /> = 1.856 cm -1), integrando le aree sotto le singole) picchi infrarossi (FT-IR dopo deconvoluzione (R 2&gt; 0.95). 5 NOTA: Il metil forti vibrazioni ( <img alt="Equazione" src="/files/ftp_upload/54496/54496eq_rho_ip_CH3.jpg" /> = 723 cm -1), provenienti dal backbone EPM, rimane invariato in caso di modifica e possono essere utilizzati come riferimento interno. </li><li> Determinare le conversioni di modifica eseguendo Analisi elementare (EA) per N, C e H sui campioni di gomma lavati e asciugati. 5 NOTA:I contenuti molari possono essere derivate dalle percentuali di massa misurati. Il contenuto di azoto molare EPM-g-furano è uguale a quella dei gruppi furano innestati. La conversione può essere calcolato confrontando il rapporto molare fra monomero MA innestate con i monomeri non innestate EPM nel precursore EPM-g-MA (7,69 x 10 -3) con il rapporto molare N: EPM della EPM-g- campione di furano. </li><li> Misurare la durezza Shore A dei campioni stampati a compressione di almeno 10 volte la pressione di un durometro su un campione di gomma, che copre l&#39;intera superficie cilindrica del durometro. 5 NOTA: I campioni con uno spessore di 2 ± 0,1 mm a dovrebbero essere utilizzati per queste prove. </li><li> Misurare l&#39;allungamento (a rottura) e il carico di rottura eseguendo prove di trazione su campioni di circa 1 mm di spessore e 5 mm di larghezza con una lunghezza morsetto di 15 mm ed una velocità di deformazione di 500 ± 50 mm / min. Determinare il modulo di Young dalla pendenza iniziale dei stres risultanticurve s-deformazione. NOTA: per ogni misurazione, di prova di 10 campioni e di escludere due valori anomali con il più alto ed i valori più bassi. </li><li> Determinare il compression set a 23 ° C mediante compressione campioni cilindrici con uno spessore di 6 ± 0,1 mm (t 0) e un diametro di 13 ± 0,1 mm tra di piastre metalliche a 3/4 th del loro spessore iniziale (t n) per 70 hr, lasciarli rilassarsi a 50 ° C per ½ ora e misurare lo spessore (t i). NOTA: Il valore di compression set può essere determinata da (t 0 -t i) / (t 0 -t n). </li></ol> 2. Diels-Alder cross-linking e ritrattamento <ol><li> Prima dell&#39;esperimento, sintetizzare il bismaleimide alifatico (BM) da didodecylamine ed anidride maleica (MA) secondo una procedura riportata. 41 </li><li> Pesare 40,0 g di EPM-g-furano in gomma (8.6 mmol contenuti furano) e 0,04 g fenolico anti-oxidant (ottadecil-1- [3,5-di-t-butil-4-idrossifenil] propionato) e dissolvere in un grande bicchiere chiuso con 500 ml di THF a 23 ° C. </li><li> Aggiungere 1,48 g del bismaleimide alifatico (4,3 mmol, 0,5 eq. In base al contenuto in furano EPM-g-furano) per becher con la soluzione al 10% in peso. </li><li> Mescolare la miscela di reazione per almeno 1 ora a 50 ° C nel contenitore chiuso, quindi rimuovere il tappo per aprire il sistema per evaporare il solvente. L&#39;evaporazione del THF può anche essere eseguita utilizzando un evaporatore rotante. </li><li> Essiccare il prodotto raccolto a peso costante in un forno sotto vuoto a 35 ° C. </li><li> Compressione muffa il prodotto per 30 minuti a 175 ° C e 100 bar. </li><li> Ricuocere il prodotto ottenuto depositandolo in stufa a 50 ° C per almeno tre giorni. </li><li> Tagliare la placca risultante della gomma in piccoli pezzi (0,05 g) con le forbici e lavarle accuratamente immergendole in acetone per rimuovere tutti i componenti che non hanno reagito e della muffa di compressione in un 0,1 mm di spessore film. </li><li> Registrare uno spettro infrarosso trasmissione della pellicola risultante in un supporto tablet KBr, utilizzando lo stesso set-up come descritto per 1.9.1. 5 </li><li> Determinare la conversione di reticolazione da una relativa diminuzione del COC vibrazioni tratto simmetrica degli anelli furano ( <img alt="Equazione" src="/files/ftp_upload/54496/54496eq_v-sCOC.jpg" /> = 1013 centimetri -1) come descritto in 1.10. 5 </li><li> Determinare la conversione reticolazione eseguendo EA per N, C e H sui campioni di gomma lavato e essiccato. 5 </li><li> Determinare la durezza Shore A, il modulo di Young, l&#39;allungamento a rottura, carico di rottura e compression set a 23 ° C nello stesso modo descritto in 1,12-14. </li><li> Rielaborare i campioni dopo test tagliandoli in piccoli pezzi con le forbici (± 50 mm 3) e stampaggio a compressione questi alle stesse condizioni in nuovi, campioni omogenei con le stesse dimensioni. </li></ol><ol><li> Scaldare un miscelatore discontinuo interna a 70 ° C e lasciarla ruotare a 50 rpm. NOTA: Un passo condizionamento iniziale svuotando la camera con azoto offre un migliore controllo dei processi di reticolazione. </li><li> Feed 18,1 g di ENB-EPDM (48% in peso di etilene, 5,5% in peso ENB) al miscelatore discontinuo interna per raggiungere un fattore di riempimento del 70% e miscelare per 2 minuti per ottenere una massa fusa omogenea. </li><li> Feed 1.25 phr di perossido di (terz-butilperossi-isopropil) benzene) o 1,88 phr di un 80% puro, standard, semi-efficiente sistema di vulcanizzazione di zolfo e mescolare con la gomma per 3 minuti a 70 ° C. </li><li> Compressione stampo composto risultante in una pressa a caldo per 30 minuti a 175 ° C e 100 bar per curare esso. </li><li> Determinare la durezza Shore A, il modulo di Young, l&#39;allungamento a rottura e il massimo di compressione resistenza alla trazione impostata nello stesso modo come descritto nel 1,12-14. </li></ol> 4. Cross-link Determinazione della densità <ol><li> Tagliare un pezzo di modellato compressione, di gomma reticolata di circa 50 mg con le forbici. <ol><li> Determinare il peso iniziale del campione di gomma appunto per pesata in una fiala di vetro da 20 ml (W 0). </li><li> Immergere la gomma pesato in 15 ml di decalina. </li></ol></li><li> Sia la gomma si gonfiano in decalina fino suo peso non aumenta più e l&#39;equilibrio gonfiore è raggiunto (circa 3 giorni). </li><li> prendere con cautela il campione gonfio dal flaconcino e tamponare accuratamente la superficie con un panno di carta per rimuovere qualsiasi solvente dalla superficie senza schiacciarla. </li><li> Pesare il campione di gomma gonfia in una nuova fiala del campione (W 1). </li><li> Essiccare il campione gonfia in stufa da vuoto a 80 ° C fino a peso costante e determinare il peso secco del campione (W 2). </li><li> Ottenere il contenuto di gel da W 2 / W 0 x 100% </li><li> Determinare il cross-Densità collegamento ([XLD] in mol / cm 3) usando l&#39;equazione di Flory-Rehner 42, 43, [XLD] = (ln (1-V R) + V R + χV R 2) / (2V S (0.5V R -V R 1/3)) con V S il volume molare del solvente (decalina: 154 ml / mol a 23 ° C), il parametro χ interazione (decalina-EPDM: 0,121 + 0.278V R 44) e V R del frazione di volume di gomma in campioni gonfio che può essere determinato da W 2 / (W 2 + (W 1 -W 2) ∙ ρ EPM-g-furano / ρ decalina) con le densità (P) essendo 860 kg / m 3 per EPM-g-furano e 896 kg / m 3 per decalina rispettivamente. </li></ol>

The author Martin van Duin is an employee of LANXESS Elastomers B.V. that produces EPM-g-MA rubbers used in this Article.

Una gomma EPM-g-MA commerciale era reversibile termo-reticolato in un semplice approccio in due fasi. La gomma maleated è stato modificato con FFA di innestare gruppi furani sulla spina dorsale di gomma. I furani in attesa risultanti mostrano reattività come dieni Diels-Alder. Un alifatico BM è stato usato come agente di reticolazione, risultando in un ponte termico reversibile tra due porzioni furano. Entrambe le reazioni hanno avuto successo con buone conversioni (&gt; 80%) secondo spettroscopia infrarossa, analisi...

Zolfo vulcanizzazione e perossido di polimerizzazione sono attualmente i principali tecniche industriali reticolanti nell&#39;industria della gomma, ottenendo irreversibili legami incrociati chimiche che impediscono ritrattamento melt. 1, 2 A &#39;culla alla culla&#39; approccio riciclare gomme reticolate richiede un materiale che comporta gomme simili permanentemente reticolato a condizioni di servizio, pur avendo la lavorabilità e completa riciclabilità di un termoplastico ad alte temperature. Un approccio per realizzare tale riciclabilità utilizza reti gommose con reversibili legami incrociati che rispondono ad uno stimolo esterno, come la temperatura (più fattibili dal punto di vista di future applicazioni industriali). 3-5 La formazione di questi legami incrociati relativamente bassa service temperature è necessaria per il buon comportamento meccanico della gomma, mentre la loro scissione a temperature elevate (simili a temperatura di lavorazione non reticolato composto originale) consente reCycling del materiale. Alcuni materiali specifici possono essere reversibilmente reticolato facendo uso di cosiddette reti covalenti dinamiche attraverso reazioni di policondensazione 6 o dalla cosiddetta topologia di rete reversibile congelamento tramite reazioni di transesterificazione. 7-9 Lo svantaggio di questi approcci è la necessità di progettare e sintetizzare nuovi polimeri, piuttosto che modificare esistenti, gomme commerciali che hanno già le proprietà desiderate. Tecniche per termo-reversibile gomme cross-link di coinvolgere legami idrogeno, interazioni ioniche e legame covalente, come attraverso riarrangiamenti disolfuro termo-attivato. 10-13 Recentemente, cross-linking tramite Diels-Alder (DA) la chimica è stato sviluppato termo-reversibili. 14 -21 dA chimica può essere applicata a una vasta gamma di polimeri e rappresenta una scelta popolare, in particolare poiché la reazione dA permette cinetiche relativamente veloci e condizioni di reazione blande. 17, 22-24 Thtemperature EIR accoppiamento basso e alto disaccoppiamento rendono furano e ottimi candidati Maleimide di polimeri reversibili cross-linking. 18-20, 25-28 Lo scopo del presente lavoro è di fornire un metodo per l&#39;uso di DA chimica come strumento di reticolazione termo-reversibile per un prodotto industriale di gomma (Figura 1). 5 Primo, la reattività di elastomeri idrocarburici saturi, quali etilene / propilene (EPM), deve essere aumentata. Un esempio commercialmente rilevante che facilita questo è l&#39;innesto radicali liberi perossidi avviato di anidride maleica (MA). 29-34 secondo luogo, un gruppo furano può essere innestato un tale gomma EPM maleated inserendo furfurylamine (FFA) in anidride pendente per formare un immide. 35, 36 Infine, le frazioni furano che sono quindi collegati al backbone gomma può quindi partecipare termo-reversibili chimica dA come diene ricco di elettroni. 25, 37 l&#39;elettrone-poo bis-maleimmide (BM) è un dienofilo adatto per questa reazione di reticolazione. 19, 26, 38 <img alt="Figura 1" src="/files/ftp_upload/54496/54496fig1.jpg" /> Figura 1. Schema di reazione. Innesto furano e bismaleimide reticolazione della gomma EPM-g-MA (ristampato con il permesso di 5). <a href="https://www-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/54496/54496fig1large.jpg" target="_blank">Clicca qui per vedere una versione più grande di questa figura.</a>

<table><tbody><tr><td>ENB-EPDM</td><td>LANXESS Elastomers B.V.</td><td>Keltan 8550C</td><td></td></tr><tr><td>EPM-g-MA</td><td>LANXESS Elastomers B.V.</td><td>Keltan DE5005</td><td>Vacuum oven for one hour at 175&amp;nbsp;&amp;deg;C</td></tr><tr><td>furfurylamine</td><td>Sigma-Aldrich</td><td>F20009</td><td>Freshly distillated before use</td></tr><tr><td>di-dodecylamine</td><td>Sigma-Aldrich</td><td>36784</td><td></td></tr><tr><td>maleic anhydride</td><td>Sigma-Aldrich</td><td>M0357</td><td></td></tr><tr><td>octadecyl-1-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate</td><td>Sigma-Aldrich</td><td>367079</td><td></td></tr><tr><td>bis(tert-butylperoxy-iso-propyl) benzene</td><td>Sigma-Aldrich</td><td>531685</td><td></td></tr><tr><td>tetrahydrofuran</td><td>Sigma-Aldrich</td><td>401757</td><td></td></tr><tr><td>decalin</td><td>Sigma-Aldrich</td><td>294772</td><td></td></tr><tr><td>acetone</td><td>Sigma-Aldrich</td><td>320110</td><td></td></tr></tbody></table>

the preparation and properties of thermo-reversibly cross-linked rubber via diels-alder chemistry

è dimostrato un metodo per l&#39;utilizzo di Diels Alder chimica termo-reversibili come strumento di cross-linking per i prodotti in gomma. In questo lavoro, una gomma etilene-propilene commerciale, innestati con anidride maleica, è termo-reversibilmente reticolato in due fasi. Le porzioni anidride pendenti in primo luogo sono modificati con furfurylamine innestare gruppi furano alla spina dorsale in gomma. Questi gruppi furano sospensione sono poi reticolati con una bis-maleimide tramite una reazione di coupling Diels-Alder. Entrambe le reazioni possono essere eseguite in una vasta gamma di condizioni sperimentali e possono essere facilmente applicate su larga scala. Le proprietà del materiale delle conseguenti Diels-Alder gomme reticolate sono simili a un etilene / propilene / diene gomma (EPDM) di riferimento perossido di cured. I legami incrociati rompono a temperature elevate (&gt; 150 ° C) tramite la reazione di retro-Diels-Alder e possono essere riformati mediante ricottura termica a temperature più basse (50-70 ° C). La reversibilità del sistema è stato dimostrato ingegnoh spettroscopia infrarossa, prove di solubilità e proprietà meccaniche. Riciclabilità del materiale è stato anche mostrato in modo pratico, vale a dire, tagliando un campione reticolato in piccole parti e di compressione li stampaggio in nuovi campioni visualizzazione proprietà meccaniche comparabili, che non è possibile per le gomme convenzionalmente reticolati.

La modifica riuscita dei EPM-g-MA in EPM-g-furano e reticolazione con il bismaleimide è mostrato dalla trasformata di Fourier spettrometria all&#39;infrarosso (FTIR) (Figura 2). La presenza di gruppi furano nel prodotto EPM-g-furano può dedurre dalla scissione del picco CC alifatico allungamento ( <img alt="Equazione" src="/files/ftp_upload/54496/54496eq_v-sCC.jpg" /> = 1.050 cm -1) in due picchi furano ( <img alt="Equazione" src="/files/ftp_upload/54496/544...

Watch this Scientific Journal Video about The Preparation and Properties of Thermo-reversibly Cross-linked Rubber Via Diels-Alder Chemistry at JoVE.com

The Preparation and Properties of Thermo-reversibly Cross-linked Rubber Via Diels-Alder Chemistry

A simple two-step approach involving rubber modification and cross-linking yields fully reworkable, elastic rubber products.

La preparazione e la proprietà di Thermo-reversibile reticolato Chimica Gomma Via Diels-Alder

A method for using Diels Alder thermo-reversible chemistry as cross-linking tool for rubber products is demonstrated. In this work, a commercial ...

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Dienes, Conjugated Pi Systems, and Pericyclic Reactions

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13.6K Views.  University of Groningen. A simple two-step approach involving rubber modification and cross-linking yields fully reworkable, elastic rubber products. 

Video: The Preparation and Properties of Thermo-reversibly Cross-linked Rubber Via Diels-Alder Chemistry

A Facile and Efficient Approach for the Production of Reversible Disulfide Cross-linked Micelles

Nanomedicine is an emerging form of therapy that harnesses the unique properties of particles that are nanometers in scale for biomedical application. Improving drug delivery to maximize therapeutic outcomes and to reduce drug-associated side effects are some of the cornerstones of present-day nanomedicine. Nanoparticles in particular have found a wide application in cancer treatment. Nanoparticles that offer a high degree of flexibility in design, application, and production based on the tumor microenvironment are projected to be more effective with rapid translation into clinical practice. The polymeric micellar nano-carrier is a popular choice for drug delivery applications.
In this article, we describe a simple and effective protocol for synthesizing drug-loaded, disulfide cross-linked micelles based on the self-assembly of a well-defined amphiphilic linear-dendritic copolymer (telodendrimer, TD). TD is composed of polyethylene glycol (PEG) as the hydrophilic segment and a thiolated cholic acid cluster as the core-forming hydrophobic moiety attached stepwise to an amine-terminated PEG using solution-based peptide chemistry. Chemotherapy drugs, such as paclitaxel (PTX), can be loaded using a standard solvent evaporation method. The O2-mediated oxidation was previously utilized to form intra-micellar disulfide cross-links from free thiol groups on the TDs. However, the reaction was slow and not feasible for large-scale production. Recently, an H2O2-mediated oxidation method was explored as a more feasible and efficient approach, and it was 96 times faster than the previously reported method. Using this approach, 50 g of PTX-loaded, disulfide cross-linked nanoparticles have been successfully produced with narrow particle size distribution and high drug loading efficiency. The stability of the resulting micelle solution is analyzed using disrupting conditions such as co-incubation with a detergent, sodium dodecyl sulfate, with or without a reducing agent. The drug-loaded, disulfide cross-linked micelles demonstrated less hemolytic activity when compared to their non-cross-linked counterparts.

To deliver cancer drugs to tumor sites with high specificity and reduced side effects, new methods based on nanoparticles are required. Here, we describe disulfide cross-linked micelles that can be easily prepared by hydrogen peroxide-mediated oxidation and are able to dissociate efficiently under a reducing tumor environment to release payloads.

Un approccio Facile ed efficiente per la produzione di micelle reversibile Disulfide Croce-linked

Nanomedicine is an emerging form of therapy that harnesses the unique properties of particles that are nanometers in scale for biomedical application. ...

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Synthesis of Programmable Main-chain Liquid-crystalline Elastomers Using a Two-stage Thiol-acrylate Reaction

This study presents a novel two-stage thiol-acrylate Michael addition-photopolymerization (TAMAP) reaction to prepare main-chain liquid-crystalline elastomers (LCEs) with facile control over network structure and programming of an aligned monodomain. Tailored LCE networks were synthesized using routine mixing of commercially available starting materials and pouring monomer solutions into molds to cure. An initial polydomain LCE network is formed via a self-limiting thiol-acrylate Michael-addition reaction. Strain-to-failure and glass transition behavior were investigated as a function of crosslinking monomer, pentaerythritol tetrakis(3-mercaptopropionate) (PETMP). An example non-stoichiometric system of 15 mol% PETMP thiol groups and an excess of 15 mol% acrylate groups was used to demonstrate the robust nature of the material. The LCE formed an aligned and transparent monodomain when stretched, with a maximum failure strain over 600%. Stretched LCE samples were able to demonstrate both stress-driven thermal actuation when held under a constant bias stress or the shape-memory effect when stretched and unloaded. A permanently programmed monodomain was achieved via a second-stage photopolymerization reaction of the excess acrylate groups when the sample was in the stretched state. LCE samples were photo-cured and programmed at 100%, 200%, 300%, and 400% strain, with all samples demonstrating over 90% shape fixity when unloaded. The magnitude of total stress-free actuation increased from 35% to 115% with increased programming strain. Overall, the two-stage TAMAP methodology is presented as a powerful tool to prepare main-chain LCE systems and explore structure-property-performance relationships in these fascinating stimuli-sensitive materials.

A novel methodology is presented to synthesize and program main-chain liquid-crystalline elastomers using commercially available starting monomers. A wide range of thermomechanical properties was tailored by adjusting the amount of crosslinker, while the actuation performance was dependent on the amount of applied strain during programming.

Sintesi di programmabile principale catena Elastomeri liquido-cristallini Utilizzando una a due stadi Thiol-acrilato di reazione

This study presents a novel two-stage thiol-acrylate Michael addition-photopolymerization (TAMAP) reaction to prepare main-chain liquid-crystalline ...

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Facile Synthesis of Worm-like Micelles by Visible Light Mediated Dispersion Polymerization Using Photoredox Catalyst

Presented herein is a protocol for the facile synthesis of worm-like micelles by visible light mediated dispersion polymerization. This approach begins with the synthesis of a hydrophilic poly(oligo(ethylene glycol) methyl ether methacrylate) (POEGMA) homopolymer using reversible addition-fragmentation chain-transfer (RAFT) polymerization. Under mild visible light irradiation (&#955; = 460 nm, 0.7 mW/cm2), this macro-chain transfer agent (macro-CTA) in the presence of a ruthenium based photoredox catalyst, Ru(bpy)3Cl2 can be chain extended with a second monomer to form a well-defined block copolymer in a process known as Photoinduced Electron Transfer RAFT (PET-RAFT). When PET-RAFT is used to chain extend POEGMA with benzyl methacrylate (BzMA) in ethanol (EtOH), polymeric nanoparticles with different morphologies are formed in situ according to a polymerization-induced self-assembly (PISA) mechanism. Self-assembly into nanoparticles presenting POEGMA chains at the corona and poly(benzyl methacrylate) (PBzMA) chains in the core occurs in situ due to the growing insolubility of the PBzMA block in ethanol. Interestingly, the formation of highly pure worm-like micelles can be readily monitored by observing the onset of a highly viscous gel in situ due to nanoparticle entanglements occurring during the polymerization. This process thereby allows for a more reproducible synthesis of worm-like micelles simply by monitoring the solution viscosity during the course of the polymerization. In addition, the light stimulus can be intermittently applied in an ON/OFF manner demonstrating temporal control over the nanoparticle morphology.

This article describes a process for producing polymeric self-assembled nanoparticles using visible light mediated dispersion polymerization. Using low energy visible light to control the polymerization allows for the reproducible formation of self-assembled worm-like micelles at high solids content.

Sintesi facile di micelle vermiforme dalla luce visibile mediata polimerizzazione in dispersione Utilizzando Photoredox Catalyst

Presented herein is a protocol for the facile synthesis of worm-like micelles by visible light mediated dispersion polymerization. This approach begins ...

Synthesis of Soft Polysiloxane-urea Elastomers for Intraocular Lens Application

This study discusses a synthesis route for soft polysiloxane-based urea (PSU) elastomers for their applications as accommodating intraocular lenses (a-IOLs). Aminopropyl-terminated polydimethylsiloxanes (PDMS) were previously prepared via the ring-chain equilibration of the cyclic siloxane octamethylcyclotetrasiloxane (D4) and 1,3-bis(3-aminopropyl)-tetramethyldisiloxane (APTMDS). Phenyl groups were introduced into the siloxane backbone via the copolymerization of D4 and 2,4,6,8-tetramethyl-2,4,6,8-tetraphenyl-cyclotetrasiloxane (D4Me,Ph). These polydimethyl-methyl-phenyl-siloxane-block copolymers were synthesized for increasing the refractive indices of polysiloxanes. For applications as an a-IOL, the refractive index of the polysiloxanes must be equivalent to that of a young human eye lens. The polysiloxane molecular weight is controlled by the ratio of the cyclic siloxane to the endblocker APTMDS. The transparency of the PSU elastomers is examined by the transmittance measurement of films between 200 and 750 nm, using a UV-Vis spectrophotometer. Transmittance values at 750 nm (upper end of the visible spectrum) are plotted against the PDMS molecular weight, and &#62; 90% of the transmittance is observed until a molecular weight of 18,000 g&#183;mol&#8722;1. Mechanical properties of the PSU elastomers are investigated using stress-strain tests on die-cut dog-bone-shaped specimens. For evaluating mechanical stability, mechanical hysteresis is measured by repeatedly stretching (10x) the specimens to 5% and 100% elongation. Hysteresis considerably decreases with the increase in the PDMS molecular weight. In vitro cytotoxicity of some selected PSU elastomers is evaluated using an MTS cell viability assay. The methods described herein permit the synthesis of a soft, transparent, and noncytotoxic PSU elastomer with a refractive index approximately equal to that of a young human eye lens.

This study describes synthetic routes for aminopropyl-terminated polydimethylsiloxanes and polydimethyl-methyl-phenyl-siloxane-block copolymers and for soft polysiloxane-based urea (PSU) elastomers. It presents the application of PSUs as accommodating an intraocular lens. An evaluation method for in vitro cytotoxicity is also described.

Sintesi degli elastomeri molli polisilossano-urea per applicazione di lente intraoculare

This study discusses a synthesis route for soft polysiloxane-based urea (PSU) elastomers for their applications as accommodating intraocular lenses ...

Synthesis of Terpolymers at Mild Temperatures Using Dynamic Sulfur Bonds in Poly(S-Divinylbenzene)

Elemental sulfur (S8) is a byproduct of the petroleum industry with millions of tons produced annually. Such abundant production and limited applications lead to sulfur as a cost-efficient reagent for polymer synthesis. Inverse vulcanization combines elemental sulfur with a variety of monomers to form functional polysulfides without the need for solvents. Short reaction times and straight forward synthetic methods have led to rapid expansion of inverse vulcanization. However, high reaction temperatures (&#62;160 &#176;C) limit the types of monomers that can be used. Here, the dynamic sulfur bonds in poly(S-divinylbenzene) are used to initiate polymerization at much lower temperatures. The S-S bonds in the prepolymer are less stable than S-S bonds in S8, allowing radical formation at 90 &#176;C rather than 159 &#176;C. A variety of allyl and vinyl ethers have been incorporated to form terpolymers. The resulting materials were characterized by 1H NMR, gel permeation chromatography, and differential scanning calorimetry, as well as examining changes in solubility. This method expands on the solvent-free, thiyl radical chemistry utilized by inverse vulcanization to create polysulfides at mild temperatures. This development broadens the range of monomers that can be incorporated thus expanding the accessible material properties and possible applications.

Synthesis of Terpolymers at Mild Temperatures Using Dynamic Sulfur Bonds in PolyS-Divinylbenzene

The goal of this protocol is to initiate polymerization using dynamic sulfur bonds in poly(S-divinylbenzene) at mild temperatures (90 &#176;C) without using solvents. Terpolymers are characterized by GPC, DSC and 1H NMR, and tested for changes in solubility.

Sintesi di terpolimeri a temperature miti utilizzando legami di zolfo dinamici in poli (S-divinilbenzene)

Elemental sulfur (S8) is a byproduct of the petroleum industry with millions of tons produced annually. Such abundant production and limited applications ...

Three-dimensional Biomimetic Technology: Novel Biorubber Creates Defined Micro- and Macro-scale Architectures in Collagen Hydrogels

Tissue scaffolds play a crucial role in the tissue regeneration process. The ideal scaffold must fulfill several requirements such as having proper composition, targeted modulus, and well-defined architectural features. Biomaterials that recapitulate the intrinsic architecture of in vivo tissue are vital for studying diseases as well as to facilitate the regeneration of lost and malformed soft tissue. A novel biofabrication technique was developed which combines state of the art imaging, three-dimensional (3D) printing, and selective enzymatic activity to create a new generation of biomaterials for research and clinical application. The developed material, Bovine Serum Albumin rubber, is reaction injected into a mold that upholds specific geometrical features. This sacrificial material allows the adequate transfer of architectural features to a natural scaffold material. The prototype consists of a 3D collagen scaffold with 4 and 3 mm channels that represent a branched architecture. This paper emphasizes the use of this biofabrication technique for the generation of natural constructs. This protocol utilizes a computer-aided software (CAD) to manufacture a solid mold which will be reaction injected with BSA rubber followed by the enzymatic digestion of the rubber, leaving its architectural features within the scaffold material.

An innovative biofabrication technique was developed to engineer three-dimensional constructs that resemble the architectural features, components, and mechanical properties of in vivo tissue. This technique features a newly developed sacrificial material, BSA rubber, which transfers detailed spatial features, reproducing the in vivo architectures of a wide variety of tissues.

Tridimensionale Tecnologia biomimetica: Novel Biorubber Consente di creare Definito micro e macro scala Architetture in collagene idrogel

Tissue scaffolds play a crucial role in the tissue regeneration process. The ideal scaffold must fulfill several requirements such as having proper ...

Bioingegneria

Evaluation of the Curing of Adhesive Systems by Rheological and Thermal Testing

The analysis of thermal processes associated to the curing of adhesives and the study of mechanical behavior once cured, provide key information to choose the best option for any specific application. The proposed methodology for the curing characterization, based on thermal analysis and rheology, is described through the comparison of three commercial adhesives. The experimental techniques used here are Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC) and Rheology. TGA provides information about the thermal stability and filler content, DSC allows the evaluation of some thermal events associated to the cure reaction and to thermal changes of the cured material when subjected to temperature changes. Rheology complements the information of the thermal transformations from a mechanical point of view. Thus, the curing reaction can be tracked through the elastic modulus (mainly the storage modulus), the phase angle and the gap. In addition, it is also shown that although DSC is of no use to study the curing of moisture curable adhesives, it is a very convenient method to evaluate the low temperature glass transition of amorphous systems.

An experimental methodology based on thermal and rheological measurements is proposed to characterize the curing process of adhesives with to obtain useful information for industrial adhesive selection.

Valutazione della polimerizzazione dei sistemi adesivi mediante prove reologiche e termiche

The analysis of thermal processes associated to the curing of adhesives and the study of mechanical behavior once cured, provide key information to choose ...

Ingegneria

Fabricating Degradable Thermoresponsive Hydrogels on Multiple Length Scales via Reactive Extrusion, Microfluidics, Self-assembly, and Electrospinning

While various smart materials have been explored for a variety of biomedical applications (e.g., drug delivery, tissue engineering, bioimaging, etc.), their ultimate clinical use has been hampered by the lack of biologically-relevant degradation observed for most smart materials. This is particularly true for temperature-responsive hydrogels, which are almost uniformly based on polymers that are functionally non-degradable (e.g., poly(N-isopropylacrylamide) (PNIPAM) or poly(oligoethylene glycol methacrylate) (POEGMA)). As such, to effectively translate the potential of thermoresponsive hydrogels to the challenges of remote-controlled or metabolism-regulated drug delivery, cell scaffolds with tunable cell-material interactions, theranostic materials with the potential for both imaging and drug delivery, and other such applications, a method is required to render the hydrogels (if not fully degradable) at least capable of renal clearance following the required lifetime of the material. To that end, this protocol describes the preparation of hydrolytically-degradable hydrazone-crosslinked hydrogels on multiple length scales based on the reaction between hydrazide and aldehyde-functionalized PNIPAM or POEGMA oligomers with molecular weights below the renal filtration limit. Specifically, methods to fabricate degradable thermoresponsive bulk hydrogels (using a double barrel syringe technique), hydrogel particles (on both the microscale through the use of a microfluidics platform facilitating simultaneous mixing and emulsification of the precursor polymers and the nanoscale through the use of a thermally-driven self-assembly and cross-linking method), and hydrogel nanofibers (using a reactive electrospinning strategy) are described. In each case, hydrogels with temperature-responsive properties similar to those achieved via conventional free radical cross-linking processes can be achieved, but the hydrazone cross-linked network can be degraded over time to re-form the oligomeric precursor polymers and enable clearance. As such, we anticipate these methods (which may be generically applied to any synthetic water-soluble polymer, not just smart materials) will enable easier translation of synthetic smart materials to clinical applications.

Protocols are described for the fabrication of degradable thermoresponsive hydrogels based on hydrazone cross-linking of polymeric oligomers on the bulk scale, microscale, and nanoscale, the latter for preparation of both gel nanoparticles and nanofibers.

Fabbricando degradabile Hydrogel idrogeli su scale di lunghezza Multiple tramite estrusione reattiva, microfluidica, auto-assemblaggio ed elettrofilatura

While various smart materials have been explored for a variety of biomedical applications (e.g., drug delivery, tissue engineering, bioimaging, etc.), ...

Designed for Molecular Recycling: A Lignin-Derived Semi-aromatic Biobased Polymer

The development of chemically recyclable biopolymers offers opportunities within the pursuit of a circular economy. Chemically recyclable biopolymers make a positive effort to solve the issue of polymer materials in the disposal phase after the use phase. In this paper, the production of biobased semi-aromatic polyesters, which can be extracted entirely from biomass such as lignin, is described and visualized. The polymer poly-S described in this paper has thermal properties similar to certain commonly used plastics, such as PET. We developed a Green Knoevenagel reaction, which can efficiently produce monomers from aromatic aldehydes and malonic acid. This reaction has been proven to be scalable and has a remarkably low calculated E-factor. These polyesters with ligno-phytochemicals as a starting point show an efficient molecular recycling with minimal losses. The polyester poly(dihydrosinapinic acid) (poly-S) is presented as an example of these semi-aromatic polyesters, and the polymerization, depolymerization, and re-polymerization are described.

An example of a closed-loop approach towards a circular materials economy is described here. A whole sustainable cycle is presented where biobased semi-aromatic polyesters are designed by polymerization, depolymerization, and then re-polymerized with only slight changes in their yields or final properties.

Progettato per il riciclaggio molecolare: un polimero biobased semi-aromatico derivato dalla lignina

The development of chemically recyclable biopolymers offers opportunities within the pursuit of a circular economy. Chemically recyclable biopolymers make ...

Depolymerizable Olefinic Polymers Based on Fused-Ring Cyclooctene Monomers

The growing consumption of synthetic polymers and the accumulation of polymer waste have led to a pressing need for new routes to sustainable materials. Achieving a closed-loop polymer economy via chemical recycling to monomer (CRM) is one such promising route. Our group recently reported a new CRM system based on polymers prepared by ring-opening metathesis polymerization (ROMP) of trans-cyclobutane fused cyclooctene (tCBCO) monomers. This system offers several key advantages, including the ease of polymerization at ambient temperatures, quantitative depolymerization to monomers under mild conditions, and a broad range of functionalities and thermomechanical properties. Here, we outline detailed protocols for the preparation of tCBCO-based monomers and their corresponding polymers, including the preparation of elastic polymer networks and compression molding of linear thermoplastic polymers. We also outline the preparation of high ring strain E-alkene tCBCO monomers and their living polymerization. Finally, the procedures for the depolymerization of linear polymers and polymer networks are also demonstrated.

Here, we describe protocols for the preparation of trans-cyclobutane fused cyclooctenes (tCBCO),&#160;their polymerization to prepare depolymerizable olefinic polymers, and the depolymerization of these polymers under mild conditions. Additionally, protocols for the preparation of depolymerizable networks and compression molding of rigid linear plastics based on this system are described.

Polimeri olefinici depolimerizzabili a base di monomeri cicloottini ad anello fuso

The growing consumption of synthetic polymers and the accumulation of polymer waste have led to a pressing need for new routes to sustainable materials. ...