Functionalization, block copolymerization and dispersion polymerization using anionic techniques.

摘要

The functionalization of poly(styryl)lithium with 1-butene oxide in benzene was investigated at room temperature. The functionalized polymer was characterized by SEC, 1H NMR, 13C NMR, APT-13C NMR, DEPT-13C NMR, MALDI-TOF spectroscopies, flash column chromatography and titration. Based on the results of all these methods, hydroxylated polystyrene was obtained in about 99% yield and the regioselectivity was consistent with predominantly primary addition of the 1-butene oxide unit to the poly(styryl)lithium chain end to form a secondary alcohol without oligomerization.; A series of styrene and 1-butene oxide block copolymers in benzene were prepared with lithium as counterion and polyiminophosphazene base t-Bu-P₄ {lcub}[1-tert-butyl-4,4,4-tris(dimethylamino)-2,2-bis[tris(dimethylamino)-phosphoranylidenamino]-2λ 5, 4λ5-ca-tenadi(phosphazene)]{rcub} as complexing agent. The products were characterized by SEC, HPLC, NMR, DSC and SAXS. It was shown by SEC that the copolymers exhibited apparent narrow molecular weight distributions. Although SEC revealed that the crude copolymers were contaminated with both polystyrene and poly(1-butene oxide, the amount of poly(1-butene oxide) homopolymer was below 20% when the block length of poly(1-butene oxide) was less than 30,000 g/mol. This value indicates that a much higher second block length with less compositional heterogeneity can be obtained for 1-butene oxide compared with the analogous preparation of polystyrene-b-poly(propylene oxide). Since the block copolymerization can be controlled to a large degree, it provides one more non-crystalline example for the study of microphase separation in block copolymers. The diblock copolymer of styrene and 1-butene oxide (15k–20k) exhibited two T _gs (71°C for PS block and −68°C for PBO block) and a lamellar structure (d = 280 Å).; Because of the unexpected hydrocarbon solubility of the poly(1-butene oxide), anionic dispersion polymerization of styrene in hexane was investigated using sec-butyllithium as initiator and poly[styrene- b-(1-butene oxide)] block copolymers as steric stabilizers. The size distribution and aggregation behavior of the dispersion particles were studied by SEM. The effect of block lengths and concentration of the stabilizer, additives and the concentration of the additives was studied systematically. It was observed that the dispersion not only depends on the size of poly(1-butene oxide) block, but also depends on the size of the anchor block (polystyrene). When the block length of polystyrene was 5 k, the diblock cannot provide sufficient stabilization and flocculation occurred. When the block length of polystyrene was increased to 15 k, the diblock became a useful stabilizer for dispersion polymerization. The particle size decreased from 10 to 1 μm when the concentration of the stabilizer increased from 5 wt % (compared to the monomer) to 18 wt %. Surprisingly, the presence of added lithium chloride (20 eq. with respect to monomer) resulted in the most uniform, unaggregated particles.