Molecular weight distribution graft copolymers

It is often assumed that the polymerization chemistry which occurs in the dispersed phase is identical to that which occurs in the equivalent bulk process. That assumption may be valid if the monomers and initiator are virtually insoluble in the continuous phase. Then, polymerization rates, molecular weight distributions, and copolymer compositions can be predicted from conventional kinetic schemes. But drop stabilizers may react with species inside the drops (for example, to form graft copolymers). 

The high-molecular weight was assigned to the PMMA grafted to the copolymer chains and the low-molecular weight to the PMMA initiated by the MMA radical (II). However, only one molecular weight distribution peak was observed for the PMMA initiated by the latter system, i.e., in combination with BP, which implies that only aminomethyl radicals are capable of initiating the polymerization. 

Chung and coworkers have reported on the use of stable borinale or boroxyl radicals (e.g. 114) to mediate radical polymerization." Methacrylates (MMA) and acrylates (trifluoroelhyl acrylate) have been polymerized at ambient temperature to yield polymers with relatively narrow molecular weight distributions.231233 The method has been used to prepare block copolymers and polyolefin graft copolymers.2 4 37... 

A radical initiator based on the oxidation adduct of an alkyl-9-BBN (47) has been utilized to produce poly(methylmethacrylate) (48) (Fig. 31) from methylmethacrylate monomer by a living anionic polymerization route that does not require the mediation of a metal catalyst. The relatively broad molecular weight distribution (PDI = (MJM ) 2.5) compared with those in living anionic polymerization cases was attributed to the slow initiation of the polymerization.69 A similar radical polymerization route aided by 47 was utilized in the synthesis of functionalized syndiotactic polystyrene (PS) polymers by the copolymerization of styrene.70 The borane groups in the functionalized syndiotactic polystyrenes were transformed into free-radical initiators for the in situ free-radical graft polymerization to prepare s-PS-g-PMMA graft copolymers. 

Wellons, J. D., A. Schindler, and V. Stannett Molecular weight distributions of the side chains of radiation initiated graft copolymers. Polymer 5, 499... 

Miura and coworkers and Akutsu and coworkers reacted a copolymer of styrene and 2,5-bis(methoxycarbonyl-l-hexene (87) with LDA to yield a polyenolate (88), which was active in the anionic polymerization of MMA (equation 67). When less than 1 equivalent (0.75) of LDA relative to the ester groups was used, the graft copolymer 89 was formed . When more than 1 equivalent of LDA was used, the molecular weight distribution was bimodal. Indeed, a mixture of homopolymer (PMMA) and graft copolymer (89) was formed merely because LDA is also prone to initiate the anionic polymerization of MMA . It was ascertained that the styrene units of the copolymer were not involved in the grafting reaction. ... 

Polymerization of the alkoxyallene with macromonomers having a poly (ethyleneglycol) group by [(7r-allyl)Ni(OCOCF3)]2/PPh3 produces a graft copolymer with narrow molecular weight distribution [129]. The products serve as polymeric surfactants in the polymer blend system of polystyrene and poly(methyl methacrylate). 

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