Synthesis of Poly(styrene)-b-poly(dimethylsiloxane)-b-poly(styrene) Triblock Copolymers by Iodine Transfer Polymerization in Miniemulsion

Abstract

The first synthesis of poly(styrene)-b-poly(dimethylsiloxane)-b-poly(styrene) triblock copolymer in miniemulsion has been achieved by controlled/living radical polymerization of styrene using a modified hydroxypropyl terminated poly(dimethylsiloxane) as a transfer agent for iodine transfer polymerization. First an R,ω-hydroxypropyl poly(dimethylsiloxane) was modified by esterification with 2-bromopropionic acid. The second step consisted in a nucleophilic substitution of bromine by iodine through the reaction with sodium iodide in acetone. Then, miniemulsion polymerization of styrene was performed in the presence of sodium dodecyl sulfate as surfactant, 2,2′-azobis(isobutyronitrile) as radical initiator, and the R,ω-diiodopoly(dimethylsiloxane) as both the hydrophobe and the macrotransfer agent. Stable white latexes were obtained with a good correlation between theoretical and experimental molecular weights. Considering the process and the polymerization type, rather low polydispersity indexes (around 1.7) were reached. A kinetic study showed an increase of the molecular weight with conversion. Last, a chain extension led to a shift of the molecular weight distribution giving evidence for the living character of the triblock copolymers.

Silicone containing copolymers: Synthesis, properties and applications

“…Silicone containing diblock or triblock copolymers with well-defined structures can be prepared by living anionic polymerization through the sequential addition of monomers, using ROP or ATRP.Another widely utilized method is the chemical coupling of functionally terminated blocks usually prepared by anionic polymerization. Each of these synthetic techniques and the properties of copolymers obtained will be discussed separately in the forthcoming sections.Several other methods which can also be used for the preparation of silicone containing block copolymers include free radical copolymerization using macroinitiators (21,(28)(29)(30), iodine transfer polymerization (24,31) and reversible additionfragmentation chain transfer (RAFT) polymerization (32)(33)(34). Unfortunately, some of these techniques do not provide very good control of the block lengths, may require the use of specific monomers and also may lead to extensive homopolymer contamination (29,30).…”

Synthesis and Characterization of PDMS Based Triblock and Pentablock Copolymers

“…PVAc and PSt segments exhibited T g values of 40 and 105°C [9,12,13], respectively for the The linear fit indicated that the concentration of propagating radical species is constant and radical termination reactions are not significant over time scale of the reaction. It was found that the molecular weights increase almost linearly with conversion, indicating that the number of chains was constant and the chain transfer reactions were rather negligible [16][17][18]. Thus from Fig.…”

Synthesis of Waterborne Polyurethane by the Telechelic α,ω-Di(hydroxy)poly(n-butyl acrylate)

“…The synthetic procedure was similar to the previous report [23,31]. Sodium iodide (0.08 mol) and α,α′-dibromo- p -xylene (0.03 mol) were dissolved in acetone under nitrogen.…”