The syntheses of aromatic oxazolyl and carboxyl functionalized polymers using 4,5-dihydro-4,4-dimethyl-2-[4-(1-phenylethenyl)phenyl]oxazole in atom transfer radical polymerization reactions

Abstract

The syntheses of oxazolyl functionalized polymers using 4,5-dihydro-4,4-dimethyl-2-[4-(1-phenylethenyl)phenyl]oxazole in atom transfer radical polymerization (ATRP) reactions are reported. A new oxazolyl initiator system was generated in situ by the atom transfer radical addition (ATRA) reaction of (1-bromoethyl)benzene with 4,5-dihydro-4,4-dimethyl-2-[4-(1-phenylethenyl)phenyl]oxazole and employed as the oxazolyl functionalized initiator for the polymerization of styrene by ATRP methods to produce well defined α-oxazolyl functionalized polystyrene. The polymerization kinetic data for the synthesis of α-oxazolyl functionalized polystyrene shows that the polymerization process follows first order rate kinetics with respect to monomer consumption. The number average molecular weights (Mn=0.61×103–9.8×103g/mol) of the α-oxazolyl functionalized polymers increased linearly with percentage monomer conversion and polymers with narrow molecular weight distributions (Mw/Mn=1.22–1.51) were obtained. The polymerization processes were monitored by gas chromatographic analyses to determine the extent of monomer consumption as a function of time. α,ω-Bis(oxazolyl) functionalized polystyrene was prepared by a new, controlled/living, post ATRP chain end functionalization reaction which involves the direct addition of 4,5-dihydro-4,4-dimethyl-2-[4-(1-phenylethenyl)phenyl]oxazole to the ω-terminus of α-oxazolyl functionalized polystyrene, without the isolation and purification of the functionalized polymeric precursor. The quantitative chemical transformation of the oxazoline group of the respective oxazolyl chain end functionalized polystyrene derivative by successive acid and base hydrolysis, followed by final acidification, provides the corresponding well defined aromatic carboxyl chain end functionalized polystyrene. The organic precursor compounds, the oxazolyl functionalized 1,1-diphenylethylene derivative and the functionalized polymers were characterized by 1H NMR and 13C NMR spectrometry, FTIR spectroscopy, size exclusion chromatography, thin layer chromatography and non-aqueous titration measurements.