Thermally Responsive Amphiphilic Conetworks and Gels Based on Poly(N‑isopropylacrylamide) and Polyisobutylene

Novel amphiphilic conetworks (APCN) consisting of thermoresponsive poly(N-isoproplyacrylamide) (PNiPAAm) cross-linked by hydrophobic methacrylate-telechelic polyisobutylene (MA-PIB-MA) were successfully synthesized in a broad composition range. The resulting PNiPAAm-l-PIB conetworks (“l” stands for “linked by”) were obtained by radical copolymerization of NiPAAm with MA-PIB-MA in tetrahydrofuran, a cosolvent for all the components. Low amounts of extractables substantiated efficient network formation. The composition dependent two glass transition temperatures (Tg) by DSC analysis indicate microphase separation of the cross-linked components without mixed phases. It was found that the PNiPAAm-l-PIB conetworks are uniformly swellable in both water and n-hexane; i.e., these new materials behave either as hydrogels or as hydrophobic gels in aqueous or nonpolar media, respectively. The uniform swelling in both polar and nonpolar solutes indicates cocontinuous (bicontinuous) phase morphology. The equilibrium swelling degrees (R) depend on composition, that is, the higher the PIB content, the lower the R in water and the higher in n-hexane. The PNiPAAm phase keeps its thermoresponsive behavior in the conetworks as shown by significant decrease of the swelling degree in water between 20 and 35 °C. The lower critical solubility temperature (LCST) values determined by DSC are found to decrease from 34.1 °C (for the pure PNiPAAm homopolymer) to the range of 25–28 °C in the conetworks, and the extent of the LCST decrease is proportional with the PIB content. Deswelling-swelling, i.e., heating–cooling, cycle indicates insignificant hysteresis in these new thermoresponsive materials. This indicates that PNiPAAm-l-PIB conetworks with predetermined and thermoresponsive swelling behavior can be designed and utilized in several advanced applications on the basis of results obtained in the course of this study

Organocatalytic synthesis and postpolymerization functionalization of allyl-functional poly(carbonate)s

Well-defined allyl-functional poly(carbonate)s were synthesized via the organocatalytic ring-opening polymerization of 5-methyl-5-allyloxycarbonyl-1,3-dioxan-2-one using the dual 1-(3,5-bis(trifluoromethyl)phenyl)-3-cyclohexylthiourea and (−)-sparteine catalyst system. The resulting allyl-functional poly(carbonate)s obtained showed low polydispersities and high end-group fidelity, with the versatility of the system being demonstrated by the synthesis of block copolymers and telechelic polymers. Further functionalization of homopolymers with degrees of polymerization of 11 and 100 were realized via the radical addition of thiols to the pendant allyl functional groups, resulting in a range of functional aliphatic poly(carbonate)s

Morpholine-functionalized polycarbonate hydrogels for heavy metal ion sequestration

A new six-membered carbonate functionalized with 2-(morpholin-4-yl)ethyl was synthesized and copolymerized with a poly(ethylene oxide)-based cross-linker in a controlled, organocatalyzed ring-opening polymerization process. Well-defined functionalized aliphatic polycarbonate-based hydrogels were obtained with gel fractions reaching 99%. Moreover, the gels that contained 2-(morpholin-4-yl)ethyl groups revealed stimuli-responsive properties towards pH. In the meantime, swelling properties of the hydrogels were found to be reproducible and good stability was observed in the pH range of 4–7.2, while a relatively rapid degradation occurred in more basic solution (pH = 10). ICP MS measurements of aqueous lead(II) nitrate solutions revealed that the functionalized material possessed properties to withdraw and retain lead ions from aqueous solution

Synthesis and post-polymerisation modifications of aliphatic poly(carbonate)s prepared by ring-opening polymerisation

Owing to their low toxicity, biocompatibility and biodegradability, aliphatic poly(carbonate)s have been widely studied as materials for biomedical application. Furthermore, the synthetic versatility of the six-membered cyclic carbonates for the realization of functional degradable polymers by ring-opening polymerisation has driven wider interest in this area. In this review, the synthesis and ring-opening polymerisation of functional cyclic carbonates that have been reported in the literature in the past decade are discussed. Finally, the post-polymerisation modification methods that have been applied to the resulting homopolymers and copolymers and the application of the materials are also discussed

Implementation of metal-free ring-opening polymerization in the preparation of aliphatic polycarbonate materials

Environmental concerns along with the need to develop aliphatic polycarbonate materials free of any toxic compounds have driven scientists to implement macromolecular engineering processes by replacing potentially toxic and carcinogenic metal-based catalysts traditionally used for the ring-opening polymerization of cyclic carbonates by organic compounds. This issue is of particular importance as aliphatic polycarbonates are gaining increasing credibility for biomedical applications owing to their biocompatibility and bioresorbability. This review provides a complete account of the various metal-free catalysts that has been developed so far as well as comprehensive investigations on the related polymerization mechanisms

Influence of the Macromolecular architecture on the self-assembly of amphiphilic copolymers based on poly(<i>N</i>,<i>N</i>-dimethylamino-2-ethyl methacrylate) and poly(ε-caprolactone)

International audienc

Preparation of in situ-forming poly(5-methyl-5-allyloxycarbonyl-1,3-dioxan-2-one)-poly(ethylene glycol) hydrogels with tuneable swelling, mechanical strength and degradability

This work describes the preparation of a new class of in situ-forming poly(carbonate)-graft-poly(ethylene glycol) hybrid hydrogels using ‘thiol–ene’ photoclick chemistry. Morphological study by cryogenic Scanning Electron Microscopy (SEM) revealed that the hydrogels display characteristic macroporous and microporous distributions, the ratio of which can be tuned by varying the length of the poly(ethylene glycol) linker. Controlling the side-chain length of the poly(ethylene glycol) also allows tuning of the equilibrium water uptake, water diffusion, mechanical properties and degradability. Furthermore, we demonstrate that these hydrogels are robust materials with fracture compressive strength in the range of 27–468 kPa and are readily degraded under physiological conditions between 8 and 22 days. The swelling of the gels was also found to be thermoresponsive making them potential candidates for delivery applications