Polystyrene macromonomer

Fig. 18 Copolymerization of the cyclic polystyrene macromonomer and a vinyl monomer...

The homopolymerization of o)-(4-vinylbenzyl)polystyrene macromonomers was also investigated kinetically by Asami21) under quite different conditions, namely very high amounts of initiator and high overall concentrations. Thus, the molecular weights (even if underestimated) are very low. Under these conditions, the rate of polymerization does not depend on the length of the side chains. However, these particular conditions which favour initiation and termination processes cannot be illustrative of regular polymerizations. 

The anionic homopolymerization of polystyrene macromonomers was carried out successfully. The methacrylic ester sites at the chain end do not require very strong nucleophiles to be initiated diphenylmethylpotassium was used, and the process was carried out at — 70 °C in THF solution24). The products are comparable with those obtained by free-radical polymerization. The molecular weight distribution should be narrower but this cannot be easily checked because these polymer species are highly branched and compact as already mentioned. 

The second system investigated 101) (polystyrene macromonomer and perfluoro-alkyl acrylate) is also of great interest. The polymerization is carried out in trifluoro-benzene with AIBN as the initiator to a conversion of the order of 60 %. The graft copolymer formed is soluble in a number of solvents in which the poly(perfluoro-alkyl acrylate) backbone would be insoluble, e.g. in THF and diethyl ether. The easy formation of foams indicates the low surface energy which is characteristic of fluorinated polymers. Double-detection GPC (UV and refractive index) showed that the distribution of polystyrene branches within the sample was quite uniform. 

Many researchers have attempted to make branched polystyrene in continuous bulk radical polymerization processes. Approaches involving the addition of additives to the polymerization process which lead to branching inside the polymerization reactor always lead to gel problems. Examples include addition of divinylmonomer [4], vinyl peroxides (e.g. I) [5,6], branched peroxides (e.g. II) [7], vinyl-functional chain transfer agents (III) [8], and the use of addition-fragmentation chain transfer agents that lead to the formation of polystyrene macromonomers (Figure 24.3) [9]. 

The composition of the PAA-g-PS graft copolymer reaction product and its purification, especially as far as the removal of unreacted PS-MA macromonomer by silica column chromatography is concerned, and the successful selective cleavage of the ferf-butyl ester under acidic conditions to render the graft copolyelectrolyte PAA-g-PS were analyzed by XH NMR spectroscopy and SEC. Figure 8a shows the SEC curves of the polystyrene macromonomer (PS-MA), the crude poly (ferf-butyl acrylate-gra/f-styrene) (PTBA-g-PS) and the PTBA-g-PS the polymethylacrylate (PMA) originates from esterification of the poly (acrylic acid) (PAA) obtained after complete saponification of the graft copolymer and represents the backbone. The XH NMR spectra of PSMA, PTBA-g-PS and of the final reaction product PAA-g-PS are shown in Fig. 8b. 

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. 

Scheme 76 Synthesis of polystyrene macromonomer with two condensable amine groups...

The introduction of polymerizable end groups into a polymer chain can be rather easily achieved by anionic polymerization techniques. Functional initiation or electrophilic termination are the most common ways to incorporate the active groups. Due to their wide applicability, polystyrene macromonomers will be examined separately from the other anionically prepared macromonomers. 

Table 1 summarizes the literature data on the graft copolymers prepared by polystyrene macromonomers, which were synthesized by anionic polymerization. 

Table 1. Graft copolymers prepared by polystyrene macromonomers synthesized anionically...

Polystyrene macromonomers (54) with molecular weight of 10 —10 were also prepared. Polymerization of methacrylate or vinyl chloride in the presence of 2-mercaptoethanol (55,56) and subsequent treatment of the resulting polymer with methacrolyl chloride led to methacryl end capped polymethacrylates and PVC. 

With thioglycolic acid as a chain-transfer agent, macromonomers are prepared from dimethylaminoethyl methacrylate and other acrylate and methacrylate derivatives (539). lodoacetic acid is used as the transfer agent for polystyrene macromonomers (540). 

Problem 12,1 Suggest an ef cient route, via ATRP and CuAAC reaction, for the synthesis of a (meth)acry-late terminated polystyrene macromonomer, such as tu-acryloyloxy-polystyrene (DP - 50). 

The second reported synthesis and application of 1,1-diphenylethylene macromonomers provided less ambiguous results and illustrated the potential of these macromonomers in synthesis of well-defined, hetero, three-armed, star-branched polymers [197, 198]. 1,1-Diphenylethylene-functionalized polystyrene macromonomers (74, 76) were prepared by the addition of poly(styr-yl)lithium with either l,3-bis(l-phenylethenyl)benzene (73, MDDPE) [198] or l,4-bis(l-phenylethenyl)benzene (75, PDDPE) [197] as shown in Eqs. (43) and (44) ... 

Using the silylamine-functionalized 1,1-diphenylalkyllithium initiator, 39, to polymerize styrene, the corresponding functionalized poly(styryl)lithium, 40 (see Scheme 18), was reacted with MDDPE to form the silyl-amine-functio-nalized, 1,1-diphenylethylene-functionalized polystyrene macromonomer (82) as shown in Scheme28 [212]. Less than 2% dimer formation was observed by SEC. 

Stadler and coworkers [213] have described another method for synthesis of 1,1-diphenylethylene-functionalized polystyrene macromonomers (84) as... 

Polymerization of a-norbornenyl-polystyrene macromonomer, a-NBPS, with the Schrock-type catalyst Mo(NAr)(CHtBu)(OC(CH3)(CF3)2)2 in toluene at room temperature gave polynorbornene-polystyrene diblock copolymer (118) in a quantitative yield [86] [Eq. (50)]. 

The topology of this product with a bulk hydrophobic structure inside and a hydrophilic part outside makes it particularly attractive for applications such as unimo-lecular micelles. On using the same procedure, norbor-nyl-poly(ethylene oxide)-polystyrene macromonomer was polymerized to polynorbornene-poly(ethylene oxide)-polystyrene block copolymer (121) [Eq. (53)]. 

Fig. 3.6 SEC curves of linear polystyrene macromonomers prepared via ATRP using bpy, PMDETA, ME TREN as ligand, respectively, and curve 1-5, 6 9. 10-15 correspond to entry i-5,6-9, 70-75 in Table 3.1...

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