Polystyrene 1 methacryloyl macromonomers

The synthesis and purification of polystyrene methacryloyl macromonomers (PS-MA) in the molecular weight range Mn= 1000-2000 g mol 1 by living anionic polymerization of styrene (S), termination with ethylene oxide (EO), and subsequent reaction with methacrylic chloride has already been described in detail elsewhere [180] (see also Scheme 16). In this context it has to be emphasized that the hydroxyethyl-terminated PS-MA macromonomer precursor (PS-OH) as obtained after purification of the crude PS-OH by silica column chromatography (cyclohexane/dichloromethane 1/1 v/v) and as charged in the PS-MA synthesis still contains up to about 15 wt-% of non-functionalized polystyrene (PS-H). This PS-H impurity of the PS-MA macromonomer does not interfere with the PS-MA synthesis and the subsequent TBA/PS-MA copolymerization and is easily and conveniently removed from the resulting PTBA-g-PS graft copolymer (see below). 

Since the pioneering work of Tsukahara on the homopolymerization of methacryloyl end-functionalized polystyrene macromonomers to polymacromonomers several chemically different polymacromonomers were successfully synthesized [106-118]. Also different routes to cylindrical brush polymers by grafting from [119-121] and grafting on to [122, 123] techniques were reported, each of which exhibits certain advantages and disadvantages, as outlined in Table 3. 

The synthesis of polystyrene-g-polytetrahydrofurane [188] was achieved by ATR copolymerization of methacrylic PTHF macromonomer, MA-PTHF, with styrene (Scheme 105). The PTHF macromonomer was synthesized by cationic ring opening polymerization of THF with acrylate ions, formed by the reaction of methacryloyl chloride and AgC104. The polydispersity indices of the graft copolymers determined by SEC ranged between 1.3-1.4. Kinetic studies revealed that the relative reactivity ratio of the macromonomer to St was independent of the molecular weight of PTHF. 

Tanaka et al. used NPLC and RPLC to determine CCD of PMMA- -PS with different compositions and conversions synthesized from the copolymerization of methyl methacrylate and co-p-vinylbenzyl polystyrene macro monomer [ 158]. The good agreement between CCD obtained by both HPLC modes showed that the molecular weight effect on the CCD is negligible. As the macromonomer content increases, the CCD becomes sharper. These results are in accordance with the theoretical predictions. As the conversion increases at the same feed composition, the CCD becomes broader towards the low macromonomer content side, which is in contrast to the CCD of the samples obtained previously from oo-methacryloyl polystyrene macro monomer [159]. They also showed that the CCD is broadened as the graft length increases, in copolymer samples with a similar composition, in accordance with the theoretical prediction [159]. 

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