Laura Jonckheere

Providing polyurethane foams with functionality: a kinetic comparison of different “click” and coupling reaction pathways

For high-tech applications, polyurethane (PU) materials require additional surface properties and functionality, which can be achieved by incorporation of “clickable” groups in the PU structure, allowing for polymer post-modification via chemical coupling with desired molecules. Therefore, in this study, various “click” and coupling reactions, consisting of the copper(I) catalyzed Huisgen 1,3-dipolar alkyne–azide, thermally and photo-initiated thiol–ene/thiol–yne and Diels–Alder reactions, have been used for surface functionalization of PU foams. As a result of diffusional effects, the reaction rate was considerably depressed and thus, the reaction parameters, including the temperature and the concentration of reagents and the “click” compound, were optimized for each click/coupling approach to obtain high functionalization yields. As such, a kinetic comparison study of the different chemistries used was performed, using in situ FT-IR and offline 1H NMR methods. This work not only reveals kinetic trends but also compares promising and limiting aspects of the different click/coupling pathways employed, which is envisaged to be also useful for functionalizing other cross-linked polymeric materials.

Thermosensitive polymer structures based on segmented copolymer networks

Segmented polymer networks with LCST-behavior have been prepared by free radical initiated copolymerization of α,ω-bis-methacrylate terminated poly(methyl vinyl ether) (PMVE) with 2-hydroxy ethyl methacrylate (HEMA) or butyl acrylate (BA). The PMVE bis-macromonomers have been obtained via a semi-continuous process by end-capping the living cationic polymerization of methyl vinyl ether (MVE) with HEMA. The phase separation temperature can be varied by changing the PMVE/comonomer ratio. Incorporation of PMVE-grafts in the hydrogels increases the rate of deswelling and improves the mechanical properties. The application of the segmented networks for thermo-controllable solid phase extraction has been demonstrated by their thermosensitive adsorption behavior of toluene from a water solution.

Thermo-responsive solid-phase extraction using poly(methyl vinyl ether)-containing Segmented polymer networks

Segmented polymer networks containing poly(methyl vinyl ether) (PMVE) segments were prepared by free-radical-initiated copolymerization of PMVE-α,ω-dimethacrylate with styrene or 2-hydroxyethyl methacrylate (HEMA). These networks were evaluated as thermo-responsive solid-phase extraction materials. Suspension-derived polymer networks consisting of 80% of PMVE and 20% of HEMA adsorb toluene from an aqueous solution at 40°C and release the adsorbed toluene quantitatively at 20°C.

Thermotropic Networks Based on Poly(Methyl Vinyl Ether)

Segmented polymer networks consisting of poly(methyl vinyl ether) (PMVE) and a second polymer were synthesized by copolymerization of PMVE-α,ω-bis-methacrylate with a hydrophilic vinyl monomer (hydroxyethyl methacrylate, HEMA) or a hydrophobic vinyl monomer (styrene, St or butyl acrylate, BA). Such networks, swollen to equilibrium in water, show thermotropic properties in the case of the PMVE-PSt and PMVE-PBA systems due to the lower critical solution temperature (LCST) properties of the PMVE segments. The PMVE-PHEMA networks showed an inverse thermotropic behavior, i.e., the swollen networks are turbid at lower temperature and become transparent at higher temperature. The PMVE-PSt networks containing a small fraction of PSt are the best materials for thermotropic properties because the swelling is limited to a few percent which results in materials free of cracks after repeated heating–cooling (with corresponding de-swelling–swelling) processes.

Functional segmented polymer networks based on polytetrahydrofuran and poly(vinylbenzyl chloride)

Abstract Functional segmented polymer networks (FSPNs) were synthesised via free radical initiated copolymerisation of polytetrahydrofuran (PTHF) bis-macromonomers with vinylbenzyl chloride (VBCl). The purpose of this work was to create FSPNs, providing supports with a functional group that can be substituted and may serve to immobilise other reagents such as catalysts. After the preparation and detailed characterisation of several PTHF bis-macromonomers, FSPNs were prepared with varying molecular weight of the PTHF chain and varying PTHF/ PVBCl ratio. Measurements of the soluble fraction and elemental analyses demonstrated that FSPNs with a wide composition range could be prepared. From dynamic-mechanical and thermal analyses, it could be concluded that most FSPNs showed some degree of compatibility and complete absence of crystallinity. The mechanical properties of the FSPNs are directly related to their composition. The degree of substitution of all networks is close to quantitative.