Allyl-terminated polystyrenes (PS macromonomers) were synthesized by quasiliving atom transfer radical polymerization (ATRP) of styrene followed by carbocationic chain end transformation with allyltrimethylsilane in the presence of titanium tetrachloride. Systematic investigations were carried out on metallocene/MAO-catalyzed copolymerization of PS macromonomers with propene by varying the molecular weight of the macromonomer, the type of catalyst, the polymerization temperature, and the propene pressure. The resulting poly(propene-g-styrene) (PP-g-PS) graft copolymers were analyzed by 1 H and 13 C NMR spectroscopy, gel permeation chromatography, and differential scanning calorimetry. Macromonomer incorporation, molecular weight, tacticity, and crystallinity of the resulting PP-g-PS copolymers were greatly influenced by the investigated parameters. The macromonomer incorporation depends mostly on the polymerization temperature. The highest comonomer incorporation (10.8 wt %) was achieved at the highest polymerization temperature, but at the same time the molecular weight decreases strongly with increasing polymerization temperature leading to graft copolymers with relatively low molecular weights. For the first time, the effect of well-defined PP-g-PS grafts was investigated on blending incompatible polypropylene with polystyrene. Surprisingly, it was found that PP-g-PS graft copolymers with short PS side chains show a better compatibilization efficiency than those with long PS chains at comparable composition as scanning electron microscopic investigations on the morphology of blends indicate.

The synthesis of well-defined poly(propylene-g-styrene) (PP-g-PS) graft copolymers was investigated by metallocene catalyzed copolymerization of propylene and allyl-terminated polystyrene macromonomer (PS-allyl) obtained via quasiliving atom transfer radical polymerization (ATRP) and subsequent carbocationic allylation. It was found that the structural parameters of PP-g-PS can be controlled in a broad range by the variation of reaction conditions. At low conversion the number of polystyrene side chains per 1000 propylene units is proportional to the feed concentration of the PS-allyl macromonomer, while the length of polypropylene backbone decreases with increasing feed concentration. The number-average molecular weight (M n) of PS-allyl determines the side chain length, but it also affects the side chain density and backbone length. Both decrease with increasing M n of the macromonomer. At constant pressure, by ensuring the constant concentration ratio of propylene to PS-allyl, the PP backbone length can be varied by alteration of temperature while the side chain density remains nearly uniform. This semicombinatorial library of structural parameters vs reaction conditions affords designed synthesis of PP-g-PS graft copolymers with predetermined structure, that is, with desired length of the PS side chains, grafting density, and length of the PP backbone.

Polyisobutylene-graft-polystyrene (PIB-g-PSt) was synthesized by quasiliving atom transfer radical polymerization (ATRP) of styrene. The ATRP process was induced by an industrially produced poly-(isobutylene-co-p-methylstyrene-co-p-bromomethylstyrene) macroinitiator (PIF3) in the presence of CuBr and 2,2'-bipyridine. Successful graft polymerizations were performed both in bulk and in xylene solution.Preliminary investigations indicate phase-separated morphology and thermoplastic elastomer (TPE) behavior of this new graft copolymer with certain PIB/PSt ratios. These materials are able to elongate to ca. 500% of their original dimension without any irreversible deformation.