Possibilities and Limitations of Cationic Polymerisation in the Presence of Water

242 p.In this thesis, the possibilities and limitations of conducting cationic polymerisation of vinylic monomers in the presence of water are explored. Revisiting a large amount of work in the literature has shown that previous reports of cationic polymerisations in aqueous media leading to high molecular weights actually proceed via a radical mechanism. Based on theoretical arguments backed up by experimental data, it is shown that cationic polymerisation in water is in fact limited to the synthesis of low molecular weight polymers due to a combination of intrinsic chain transfer reactions that occur at ambient temperature and reactions with water. Following these results, the use of water-tolerant catalyst systems in wet solution is explored. The synthesis of low molecular weight poly(ß-pinene) to be used as tackifiers in the formulation of pressure-sensitive adhesives as well as the controlled polymerisation of polystyrene and poly(p-methoxystyrene) using reversible addition-fragmentation chain transfer cationic polymerisation under mild conditions is studied.Polyma

Cationic polymerization of β-pinene using B(C6F5)3 as a Lewis acid for the synthesis of tackifiers in pressure sensitive adhesives

β-pinene is a well-known bio-based monomer that can be polymerized via cationic polymerization to give low molecular weight resins that find use commercially as tackifiers. However, the controlled synthesis of these polymers by cationic polymerization is challenging due to the reactivity of commonly used Lewis acid catalysts and the propagating carbocationic species with water. Here, the cationic polymerization of β-pinene under mild conditions using the water stable Lewis acid tris(pentafluorophenyl)borane is demonstrated. It is shown that when combined with a suitable alcohol initiator the molecular weight of the polymer can be tuned while the kinetics are largely controlled by the concentration of tris(pentafluorophenyl)borane. The final poly(β-pinene) is shown to perform well as a tackifier in the formation of pressure sensitive adhesives based on polystyrene-b-polyisoprene-b-polystyrene triblock copolymers.N.B. acknowledges the financial support obtained from the Basque government (PI2017-59). The authors thank for technical and human support provided by SGIker of UPV/EHU and European funding (ERDF and ESF). D.E.M.-T. acknowledges financial support from “Ministerio de Ciencia, Innovación y Universidades” (MCIU), via a “Juan de la Cierva – Incorporación” grant (IJCI-2017-31600).Peer reviewe

Interplay of Thermosensitivity and pH Sensitivity of Amphiphilic Block–Gradient Copolymers of Dimethylaminoethyl Acrylate and Styrene

International audienceovel pH- and thermoresponsive amphiphilic diblock copolymer, comprising hydrophilic poly(2-dimethylaminoethyl acrylate) (PDMAEA) and amphiphilic poly(styrene-grad-2-dimethylaminoethyl acrylate) (P(S-grad-DMAEA)) blocks, was synthesized by nitroxide-mediated radical polymerization. A series of copolymers (PS-grad-PDMAEA) with controlled molar masses and low dispersities over a wide range of monomer feed ratios (0 < fS,0 < 1) were synthesized. Both conventional linearization and nonlinear least-squares methods were applied to estimate reliable values of the reactivity ratios for S and DMAEA radical polymerization. The calculated values of the reactivity ratios (rDMAEA = 0.25 and rS = 1.15) perfectly fitted the drift in monomer feed ratio versus conversion, showing a gradient distribution along the copolymer chains. The self-assembling behavior of the copolymers in the aqueous medium was investigated by dynamic light scattering and small-angle neutron scattering over a wide range of pH, temperature, and salt concentration. These block-gradient copolymers show reversible self-association into micelle-like structure (Dh ∼ 20 nm) in aqueous solutions triggered by both pH and temperatur