Poly(N-allyl acrylamide) as a Reactive Platform toward Functional Hydrogels.

The synthesis of poly(N-allyl acrylamide) (PNAllAm) as a platform for the preparation of functional hydrogels is described. The PNAllAm was synthesized via organocatalyzed amidation of poly(methyl acrylate) (PMA) with allylamine and characterized by 1H NMR spectroscopy, size exclusion chromatography (SEC), and turbidimetry, which allowed an estimation of the lower critical solution temperature of ∼26 °C in water. The PNAllAm was then used to make functional hydrogels via photoinitiated thiol-ene chemistry, where dithiothreitol (DTT) was used to cross-link the polymer chains. In addition, mercaptoethanol (ME) was added as a functional thiol to modulate the hydrogel properties. A decrease of the volume-phase transition temperature of the resulting hydrogels was observed with increasing ME content. Altogether this work introduces a straightforward way for the preparation of PNAllAm from PMA and demonstrates its value as a reactive polymer platform for the generation of functional hydrogels.

Selective Solvolysis of Bio-Based PU-Coated Fabric.

Polyurethane (PU) coatings are widely applied on high performing textiles due to their excellent durability and mechanical properties. PUs based on renewable resources were developed to improve the environmental impact of coatings by decreasing the carbon footprint. However, at the end-of-life, PU-coated textiles still end up as landfill or are incinerated since PUs are not biodegradable and are not being recycled at this moment. Therefore, the recycling of PU-coated substrates needs to be examined. This study reports the selective solvolysis of a polyester (PET) fabric coated with a bio-based PU using a 70% ZnCl2 aqueous solution. This method allowed the easy separation of the coating from the fabric. The thermal, chemical and mechanical characteristics of the virgin PET and recycled PET were examined via tensile strength tests, IR, TGA, DSC and GPC. Analysis of the fractions after solvolysis revealed that the PU was converted into the original polyol and an amine, corresponding to the isocyanate used for PU synthesis.

Accelerated Post-Polymerization Amidation of Polymers with Side-Chain Ester Groups by Intramolecular Activation.

The catalytic conversion of esters to amides represents new opportunities in the synthetic diversification and upcycling of polymers, as esters are commonly featured in various polymer structures. Yet, direct amidation is typically hampered by poor reaction kinetics and the effects of polymer structure on the reactivity remain poorly understood. We report the accelerated amidation for amines with additional hydrogen bond donating or accepting groups. These amines facilitate the expeditious (co)amidation of polymers with pendant ester groups, displaying at least a 400-fold higher reactivity relative to polyesters with esters in the main chain. Furthermore, a positive correlation between the reactivity and degree of polymerization for poly(methyl acrylate) suggests a hydrogen-bond mediated intramolecular activation of the esters, which was confirmed by FT-IR spectroscopy and basic molecular mechanics modeling. The reported method paves the way to synthesize diverse (co)polymers with amide side chains from readily available polymeric precursors.