PMOS-IBVE block polymers

The existence of the long-lived intermediate was also supported by the formation of pMOS-IBVE block polymers. Table 10 summarizes pertinent data for the block polymerization of IBVE from propagating poly(pMOS) obtained with iodine In CCI4, a nonpolar solvent, 40 to 50 % of the reacted IBVE is incorporated into the block polymer, whereas little block polymer is produced in the polar CH2CI2. 

Since it was considered less difficult to suppress side reaction in the pMOS polymerization due to the stabilization of the growing carbocation, cationic polymerization of pMOS was investigated in detail using iodine. The MWDs of product polymers became unimodal in the polymerization in CCI4 at 0 °C. A nearly linear relationship was observed between the peak molecular weight of the product polymers and monomer conversion, indicative of polymerization mediated by long-lived active species. At -15 °C, the of product polymers increased in almost direct proportion to monomer conversion after the second feed of pMOS. Moreover, block copolymers with IBVE were obtained under similar conditions. 

Thus, by lowering solvent polarity (CH2Cl2/CCl4 mixtures) or by the addition of a common ion salt (rtBtuNI), these researchers obtained poly(pMOS) of unimodal and relatively narrow MWDs, whose shape and position corresponded to those of the lower polymer population in the two-peaked distribution. Under these conditions the number-average molecular weights increase with conversion. Upon sequential addition of fresh monomer feeds, and block copolymers of pMOS and isobutyl vinyl ether (IBVE) are obtained [52], Similar results were also obtained for the polymerization of IBVE [53,54]. 

The first example of an AB block copolymer with a narrow MWD, prepared by cationic polymerization, was reported in 1984. ° The synthesis started with the polymerization of IBVE or MVE using the HI/Ij initiating system in toluene at -35 C. To the resulting living polymer, a solution of cetyl VE (CVE CH2=CH-0-CisH33) or pMOS in CCI4, the second monomer, was added. Then, the polymerization temperature was raised to -15 °C for complete consumption of the second monomer. 

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