Styrene-diphenylethylene copolymers

As fully described below, sPS has been found to be miscible with aPS, PPE, PYME, TMPC and styrene-l,l-diphenylethylene copolymer. Generally the reported investigations deal with the effect of the second component on crystalline features of sPS, such as polymorphic behavior, crystallization kinetics, morphology and growth rate of crystallites. Just one study reports on toughening sPS by adding suitable components. 

Gausepohl et ah [31] investigated the behavior of blends between sPS and random styrene-l,l-diphenylethylene copolymers obtained by anionic synthesis. The blends were miscible for copolymer contents of 1,1-diphenylethylene lower than 15 wt% as indicated by the occurrence of a single Tg (114°C). Tm and crystallization rate were not influenced. 

Further studies were directed to examine different SCBs and the effect of different counterions. Potassium counterions provide improved efficiency as compared to lithium or sodium counterions. The most efficient system in terms of formation of carbanions was achieved with diphenylsilacyclobutane in combination with potassium tert-butoxide and diphenylethylene <2004MI856>. Di-block copolymers from ethylene oxide and methyl methacrylate (or styrene) were synthesized by this method with 85% efficiency (Scheme 14) <2004MI856>. 

Copolymerization between an oxonium ion type monomer and a carbonium ion type monomer has never been carried out successfully. Styrene (St) does not form a copolymer with THF (1), BCMO (1), or /3-PL (2, 16). The formation of a homopolymer mixture was confirmed for the St-/ -PL system (18,19, 26). The reason for the absence of cross propagation was discussed elsewhere (6), but the reaction of the trityl cation with fi-PL and the reaction of the triethyloxonium ion with 1,1-diphenylethylene did show the absence of the bonding reaction (6). 

In a practical sense the hydrocarbon monomers that work best in anionic systems are styrene, a-methylstyrene, p-(tert-butyl)styrene, butadiene, isoprene, 2,3-dimethyIbutadiene, piperylene, stilbene, and 1,1-diphenylethylene. The latter two monomers give rise to alternating copolymers with other dienes but do not homopolymerize. Among the polar monomers (C) that can be polymerized are such monomers as 2-vinyIpyridine, pivalolactone, methacrylonitrile, methyl-methacrylate, ethylene oxide (not with Li-counterion), ethylene sulfide, and propylene sulfide. However, polymerization of many of these polar monomers suffers from side reactions and complicating termination or transfer reactions not present in the... 

In contrast to block copolymers of two methacrylates, block copolymers of a methacrylate and styrene can only be prepared anionically by polymerizing styrene first. As shown in Scheme 25, well-defined (pdi = 1.03-1.11) diblock copolymers of styrene and 6- [4 -(4"-Methoxyphenyl)phenoxy]hex-yl methacrylate (PS - PMPPHM) were synthesized directly by sequential anionic polymerization of styrene and then the methacrylate in THF at -78 °C using 5-butyl lithium as the initiator [44]. The reactivity of the growing polystyrene anions were reduced by reaction with 1,1-diphenylethylene be-... 

Along these lines of thinking block copolymers of styrene and 6-[4-(4-methoxyphenyl)phenoxy]hexylmethacrylate (MPPHM) were synthesized by anionic polymerization. Styrene was polymerized first in benzene using 5-BuLi as the initiator. After completion of polymerization the living PSIi chains were end-capped with diphenylethylene and the solvent was changed to THE Anhydrous liCl was introduced to the reactor, and the temperature was lowered to - 40 °C. At that temperature a solution of purified MPPHM in THE was introduced slowly. After complete reaction of the liquid crystalline monomer, polymerization was terminated with methanol . The procedure is outlined schematically in Scheme 9. 

For example, methyl methacrylate block copolymers are much less studied than those of styrene. Anion chain transfer occurs at the pendent ester group, drastically reducing the yield of block copolymers. Poly(methyl methacrylate-b-isoprene) has been prepared, however, by using an ingenious chain cap of l,l -diphenylethyl-ene(27,28). i l diphenylethylene will not anionically homopolymerize, therefore it adds only one mer to the macroanion. This anion is more stable in the presence of methyl methacrylate, but will initiate further polymerization. Other workers have reported the preparation of isoprene-methyl methacrylate block copolymers by sequential addition to "living" polyisoprene anions(29,30),... 

The synthesis of the poly[styrene-6-(hydroxystyrene-g-ethylene oxide)-6-styrene] (25), P[S-6-(HS-g-EO)-6-PS], has been reported. The backbone was a triblock copolymer, poly(styrene-6-t-butoxystyrene-6-styrene) (8), prepared by anionic polymerization by sequential addition of monomers. The protected t-butyl group was removed by treatment with HBr leading to the formation of P(S-6-HS-b-S) triblocks (9) (eq. 11). The metallation of the hydroxyl groups was performed in THF using either cumyl potassium or diphenylethylene potassium (eq. 12). The addition of EO generated the block graft copolymers (eq. 13). 

Because DPE cannot homopolymerize, its monomer reactivity ratio is zero, i.e., k22=0. When 1,1-diphenylethylene copolymerizes with styrene or dienes, an alternating-type copolymer is obtained (rir2=0) [125]. 

The living anionic polymers of protected functional methacrylate monomers herein introduced are very similar in reactivity and stability to those of MMA. Accordingly, these living polymers can initiate the polymerization of MMA, tBMA, and other protected functional methacrylate monomers, resulting in block copolymers with tailored chain structures. Complete aossover block copolymerizations among these methacrylate monomers are possible. Furthermore, living anionic polymers of styrene, a-methylstyrene, isoprene, and 1,3-butadiene initiate the polymerization of protected functional methacrylate monomers to afford well-defined AB diblock copolymers. In order to avoid ester carbonyl attack by the chain-end anions, the living anionic polymers should be end-capped with 1,1-diphenylethylene... 

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