- Chloro-styrene And Methyl Acrylate Gradient Copolymer Microstructure Characterization

Triad microstructures of gradient copolymers of p-chlorostyrene (S) and methyl acrylate (M) polymerized via atom transfer radical polymerization (ATRP) were studied by Nuclear Magnetic Resonance (NMR) and instantaneous propagation probabilities, which calculated from Mayo-Lewis formulas and denote a probability of a formed at the end of polymer chain under the different points of conversions. The NMR results showed that in the copolymers the monomer contents of S and M gradually decreased and increased, respectively with the conversions, while those of triads manifested different trends of changes with conversions. In the calculation results, MSS/SSM, SMS, SSS monotonously decreased and MMM increased, but MSM and SMM/MMS increased to a maximum with conversions and decreased afterwards. The tendencies of the M-centered triads' fraction with conversions obtained from the NMR experiments are consistent with that from the calculations of instantaneous propagation probabilities. This consistency is also manifested in the studies of gradient copolymers of p-FSt/MA. These two methods could be compensated in the triad microstructure elucidation of polymers.DM2002 which is a program to model the spectrum of the NMR peak is used to calculate and integrate the areas of the different peaks of the carbonyl carbon in the p-ClSt/MA gradient copolymers. It is found that the modeling spectrum is more precise to the real spectrum when using seven peaks than using three peaks. These seven peaks were accordingly assigned to M-centered pentad sequences based on similarities in chemical shifts, tendencies of change with conversions and calculations of the instantaneous propagation probability.