Poly(propylene-g-styrene) Graft Copolymers with Well-Defined Microstructure by Metallocene Catalyzed Copolymerization of Propylene with Allyl-Terminated Polystyrene Macromonomers

Abstract

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.

Preparation of highly branched polyethylene using (α‐diimine) nickel complex covalently supported on modified SiO2

“…In an opposite situation, that is, when the reactivity of the polymerizing group of the macromonomer is much lower than that of the low molecular weight comonomer, networks with high efficiency would not be formed under usual polymerization conditions. Considering that the apparent reactivity of a macromonomer decreases with its increasing molecular weight,29–39 lower than theoretical but still sufficient incorporation of PTHFDMA was expected in the PVIm‐ l ‐PTHF conetworks. Indeed, as reported by us previously,1 radical copolymerization of VIm and PTHFDMA with M n = 2170 resulted in conetworks with PTHF content higher than that in the feed for a broad range of composition.…”

“…So far, conetworks prepared by the utilization of PTHF as cross‐linker1, 24, 25 have been obtained with PTHFDMAs of relatively low molecular weights in the range of 2000–3800. As the increase of the molecular weight of macromonomers usually leads to the decrease of their apparent reactivity in copolymerization reactions,29–39 it was expected by us that increasing the molecular weight of PTHFDMA would yield conetworks with decreasing PTHF contents in comparison to that of the corresponding conetworks with lower molecular weight PTHFDMAs. For a series of conetworks with three different PTHFDMAs, the feed compositions, the amount of extractables in tetrahydrofuran (THF) and methanol (MeOH), the composition of the resulting extracted conetworks determined by elemental analysis, and the average molecular weight ( M c ) of PVIm between two cross‐linking points are presented in Table 1.…”

“…As it has been reported in several studies on the copolymerization behavior of monofunctional macromonomers, in addition to the reactivity ratios of the comonomer units, that is, that of the low molecular weight counterpart of the terminal polymerizable group of the macromonomer and the other comonomer, several other factors, such as overall concentration, viscosity of the reaction medium and molecular weight of the macromonomer influence its apparent reactivity, and thus the structure of the resulting graft copolymers 39–44. It has been found that increasing the molecular weight of monofunctional macromonomers decreases their apparent reactivity in copolymerizations in most of the cases,29–39 and only few cases have been reported with unchanged40, 41 or increased42 reactivities with increasing molecular weights. As conetwork formation with telechelic macromonomers and the composition of the resulting conetworks are expected to depend strongly on the reactivity of the telechelic macromonomers, the effect of their molecular weight in this process is of paramount importance.…”

“…Monofunctional macromonomers with one terminal polymerizable group are frequently used to prepare graft copolymers via copolymerization with low molecular weight monomers (see e.g., refs 28–44. and references therein).…”

Well-defined graft copolymers: from controlled synthesis to multipurpose applications

“…31,32 Schulze et al combined the grafting-through strategy, ATRP, and metallocene/methylaluminoxane (MAO)-catalyzed copolymerization to synthesize well-defined graft copolymers containing poly(propylene) (PP) and polystyrene segments. 33 PS segment was first prepared by ATRP and its Br chain end was converted into allyl functional group via carbocationic chain end transformation using allyltrimethylsilane in the presence of TiCl 4 . The target graft copolymers were obtained by the copolymerization of allyl-terminated PS macromonomer and propene using metallocene/MAO as catalyst.…”