Direct synthesis of amphiphilic random and block copolymers of p-hydroxystyrene and p-methoxystyrene via living cationic polymerization with BF3OEt2/ROH systems

This study shows that BF3OEt2 induces living cationic polymerization of p-alkoxystyrenes and their living copolymerization with p-hydroxystyrene (pHS) without protection of the phenolic group. Similar to pHS, controlled cationic polymerizations of p-methoxystyrene (pMOS) and p-tert-butoxystyrene (tBOS) were achieved by combination of the water adduct of pMOS [1; CH3CH(C6H4-p-OCH3)OH] and BF3OEt2 in the presence of a fairly large amount of water (equimolar to the monomer or 100 molar excess over BF3OEt2) in a CH3CN/CH2Cl2 mixture solvent (4/1 v/v) at 0 degrees C. The 1/BF3OEt2 initiating system also induced living random copolymerization of pHS and pMOS, where the M-n of the products increased in direct proportion to polymer yield with relatively narrow molecular weight distribution (MWDs) (M-w/M-n similar to 1.4). The copolymer compositions agreed with the calculated values from the monomer feed ratios and the conversion of each monomer. MALDI-TOF-MS analysis revealed that each monomer unit was distributed almost randomly. Sequential block copolymerization of unprotected pHS and pMOS with 1/BF3-OEt2 gave well-defined amphiphilic diblock copolymers with controlled molecular: weight and relatively narrow MWDs (M-w/M-n similar to 1.3).