Kinetics of the anionic polymerization of 2-(tertbutyldimethylsilyloxy) ethyl methacrylate

Abstract

The kinetics and the extent of side reactions of the anionic polymerization of silyl-protected 2-hydroxyethyl methacrylate, 2-(tert-butyldimethylsilyloxy)ethyl methacrylate (TBDMS-HEMA), in tetrahydrofuran (THF) were studied as a function of polymerization temperature. Lithium chloride was added in order to achieve a controlled polymerization. The results of polymerizations at various temperatures are compared with reported data for methyl methacrylate and tert-butyl methacrylate in THF. The activation energy for the studied monomer is lower compared to the other methacrylates. Gel permeation chromatography-viscosity studies show that poly(TBDMS-HEMA) exhibits a more wormlike structure in THF than other polymethacrylates, as indicated by a higher Mark-Houwink exponent, α = 1.025.

Blends of Poly(methacrylate) Block Copolymers with Photoaddressable Segments

“…No side reactions of the anionic chain end of the PMMA with the silyl group or ester linkage in the (TBDMS−OEMA) repeating unit were observed during the MMA polymerization. The enhanced stability of this silyl- protected HEMA in anionic polymerization was reported earlier by Nakahama et al and has been studied recently in detail at our laboratory . The change of the polymerization sequence of the protected HEMA and MMA monomers facilitates the extraction of a possible termination product that is formed during addition of the second monomer.…”

“…The living chain ends were terminated by adding degassed methanol. Universal calibration and the Mark-Houwink parameters of P(TBDMS) 48 were used to obtain the absolute molecular weight of the first block (P(TBDMS-HEMA)). The ratio between the PMMA and the silyl protected PHEMA segments of 2b was determined by 1 H NMR spectroscopy.…”

“…The enhanced stability of this silyl- protected HEMA in anionic polymerization was reported earlier by Nakahama et al 47 and has been studied recently in detail at our laboratory. 48 The change of the polymerization sequence of the protected HEMA and MMA monomers facilitates the extraction of a possible termination product that is formed during addition of the second monomer. The short homopolymer of PHEMA can be removed easily by precipitation of the deprotected polymer from dioxane into methanol due to the large difference in solubility compared with 2c, which possesses a large less polar PMMA segment.…”

“…tert -Butyldimethylsilyl was chosen as the protecting group for the HEMA due to a change in the sequence of monomer addition. Synthesis and reaction conditions for the anionic polymerization of tert- butyldimethylsilyloxyethyl methacrylate (TBDMS−HEMA) were similar to those reported in the literature. , First TBDMS−HEMA was polymerized at −60 °C in THF with LiCl for 60 min. The temperature was lowered to −78 °C and MMA as second monomer was added.…”