Polymacromonomers consisting of oligostyrene side chains (700 ≤ M n ≤ 5000 g/mol) and of a high molar mass polymethacrylate main chain are shown to exhibit a bottlebrush structure in that the PMA main chain adopts an extremely stiff conformation (i.e., a Kuhn statistical segment length of up to l k = 2000 Å) which is surrounded by the expanded but still flexible polystyrene side chains.

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A study of the radical polymerization of styrene macromonomers having a methacryloyl end group (MA-PSt; Aí" = 4400,12 400) and a vinylbenzyl end group (VB-PSt; Aí" = 4980,13 200) was carried out by using gel permeation chromatography with a laser light scattering detector (LS-GPC) and electron spin resonance spectroscopy (ESR). It was shown that the degree of polymerization of poly(macromonomer)s (Dp) measured by LS-GPC drastically varied with the macromonomer concentration in the feed ([M]); however, there was little difference in the Dp versus [M] curves between MA-PSt and VB-PSt of the same molecular weight. The Dp of poly(macromonomer)s was small (typically less than 10) at low [M] and increased rapidly with an increase in [M] followed by the sudden decrease to Dp = 1 at very high [M], The Dp versus [M] relationship was strongly affected by the molecular weight (Mw) of the macromonomers. These Dp versus[M] relationships were quite similar to Dp (or Rp) versus the degree of conversion relationship of the polymerization system of conventional small monomers in the presence of the gel effect. This indicated that the diffusion-controlled effect in macromonomer systems could be clearly described by [M] and Mv of the macromonomer.It was also shown that time-conversion curves of these macromonomers were monotonic and exhibited no feature of the autoacceleration effect normally observed in the polymerization system of small monomers in the presence of the gel effect. In addition, the polymerization rate (Rp) of MA-PSt was considerably greater than that of VB-PSt of the same molecular weight. ESR spectra of the propagating radical of MA-PSt and VB-PSt were measured to evaluate the concentration of the propagating radicals.From the results of ESR and LS-GPC, the propagation rate constant kp, the termination rate constant kt, and the radical lifetime rp of the macromonomers are evaluated and discussed.

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A series of tapered block polymers of styrene-butadiene (S and P series) and styrene-isoprene (K series) were prepared by anionic polymerization, and the effects of composition variation along the main chain in the tapered block polymers on microdomain structure and on linear dynamic mechanical response were investigated. It was found that the effects are generally twofold: (i) enhancement of mixing of unlike segments in the interfacial region ("interphase") between two coexisting microphases ("domains") (i.e., enlargement of the interphase), designated as "domain-boundary" effect, and (ii) enhancement of mixing of unlike segments in the domains (or domain centers), designated as "mixing-in-domain" effect. The domain morphology and linear dynamic mechanical response were found to be predicted in terms of the two effects, the relative contribution being dependent upon the primary chemical structure. The morphological and mechanical behaviors of the ideal block polymer and S series can be predicted in terms of the domain-boundary effect, while those of the P and K series are dominantly affected by the mixing-in-domain effect.