Abstract
Block copolymerization of 2โ(N,Nโdimethylamino)ethyl methacrylate (DMAEMA) with 2โhydroxyethyl methacrylate (HEMA) via atom transfer radical polymerization (ATRP) was studied in methanol using a macroinitiator method and a โoneโpotโ sequential addition method. The polymerization sequence of the two monomers strongly affected the block copolymer formation. When DMAEMA was used as the first monomer, both methods produced block copolymer samples containing significant amounts of DMAEMA homopolymer chains, because of the elimination of active halogen chainโends during the preparation of polyDMAEMA. Wellโcontrolled block copolymers with various block lengths were obtained via the macroinitiator method when polyHEMA was used as macroinitiator to initiate the polymerization of DMAEMA. The sequential addition method, in which HEMA was polymerized first with 90% conversion and DMAEMA was subsequently added, also yielded controlled block copolymers when the polymerization was carried out at room temperature with the DMAEMA conversion below 60%. Increasing the temperature to 60โยฐC promoted the copolymerization rate but the reaction suffered from gel formation. The addition of water to the system accelerated the polymerization rate, but led to the loss of the system livingness.
Gel permeation chromatograms of poly(HEMAโbโDMAEMA). The samples were prepared in methanol at room temperature with different block molecular weights using the macroinitiator method.
magnified imageGel permeation chromatograms of poly(HEMAโbโDMAEMA). The samples were prepared in methanol at room temperature with different block molecular weights using the macroinitiator method.