Compositional Sequence Determination of Acrylamide/Alkyl Acrylate Copolymers by NMR Spectroscopy

Abstract

ABSTRACT:Acrylamide/ethyl acrylate (A/E) and acrylamide/butyl acrylate (A/B) copolymers were prepared by free radical solution polymerization. Copolymer composition was determined from the nitrogen content of the copolymers. The copolymer composition data were used to determine the reactivity ratios for the copolymerization of A/E and A/B copolymer systems by Kclcn-Tiidos (KT) and nonlinear error in variables (EVM) methods. The reactivity ratios obtained are r A= 0.59 ± 0.05 and re=0.91±0.09 for A/E copolymer system and rA=0.71±0.05 and r8 =1.27±0.08 for A/B copolymer system. Microstructures in terms of the triad distribution from 13 C NMR spectroscopy were found to be in good agreement with those calculated from the theoretical models and Monte Carlo (MC) simulations. MC simulations were also used to determine the degree of polymerization of the two copolymer systems.KEY WORDS Microstructure / Acrylamide/Alkyl Acrylate Copolymers/ Nuclear Magnetic Resonance Spectroscopy / Monte Carlo Simulations / Detailed understanding of the microstructure of synthetic vinyl polymers is of fundamental and practical significance. The macroscopic physicomechanical and physicochemical properties of these materials are inherently dependent on chain microstructures. 1 • 2 Various mechanical properties of the polymers like viscous flow, refractive index, thermal expansivity, crystallization, etc. depend on the Tg of the polymers which in turn is affected by pendant groups and sequence distribution of comonomer units. 3 · 4 Acrylamide polymers are an important class of materials because of their use in many industrial applications such as base and top coats in leather industry,5 flocculants in industrial wastes, papermaking and mining, etc. Many workers have reported the reactivity ratios and microstructures of acrylamide copolymers by 1 H and 13 C NMR spectroscopy. 6 -9 The acrylamide/ethyl acrylate (A/E) and acrylamide/butyl acrylate (A/B) copolymers were synthesised by solution polymerization. The reactivity ratios and comonomer sequence distribution of A/E and A/B copolymers using 13 C NMR spectroscopy is reported in this article. EXPERIMENT ALEthyl acrylate (Central Drug House, India) and butyl acrylate (Central Drug House, India) were distilled under reduced pressure and stored below 5°C. Acrylamide (Sisco Research Laboratories, India) was recrystallized twice from chloroform. N,N-Dimethyl formamide (DMF) (Merck, Germany) was distilled and dried.A series of A/E and A/B copolymers containing different mole percent of the respective comonomers in feed were prepared by solution polymerization in DMF at 65°C using benzoyl peroxide (0.5 w/v%) as the initiator. The conversion was kept below 10% by precipitating the copolymer in water. The copolymers t To whom all correspondence should be addressed. 664were further dissolved in DMF and reprecipitated in water and vacuum dried.The copolymer composition was determined by estimating the nitrogen content of the copolymers. The C, H, and N analyses were done on a Perkin-Elmer 240C Elemen...

Engineering temperature‐sensitive poly(N‐isopropylacrylamide) polymers as carriers of therapeutic proteins

“…The final AMA content of polymers was generally proportional to the monomer feed ratio (Fig. 2), albeit slightly higher than the feed ratios which is indicative of preferential incorporation of AMAs into the designed polymers. This was in accordance with our expectations because the polymers were prepared in high yield (39-71%) and literature data indicate a high reactivity of AMAs in free radical polymerization (Brar et al, 1998;Davidenko et al, 1998). AMA incorporation was not affected by inclusion or omission of NASI during polymerization ( Fig.…”

Stability and thermodynamic parameters of interpolymer complexes of acrylamide/alkyl acrylate copolymers with poly(ethyleneimine): effects of microstructure and alkyl substituents of copolymers on interpolymer association

“…1 H} NMR spectroscopy 8) . The concentrations of the respective triads were calculated by measuring the area under the signals from the 13 C{ 1 H} NMR spectra of the A/E and A/B copolymers.…”

“…The influence of sequence distribution of the comonomer units in the respective copolymer chains on the stability of their interpolymer complexes with PEI has also been studied. The microstructure of the acrylamide/ethyl acrylate (A/E) and acrylamide/butyl acrylate (A/B) copolymers has been determined by 13 C NMR spectroscopy 8) . It is observed that, as the alkyl substituent in the acrylamide/alkyl acrylate (methyl, ethyl and butyl) is made bulkier, the stability of the complexes is affected significantly by steric factors that govern the accessibility of the reactive sites during the formation of interpolymer complexes.…”

Design of Copolymers Based on Sequence Distribution for a Targeted Molecular Weight and Conversion

“…One of the chief challenges in unraveling the relationship between sequence and properties is that experimental techniques allow some measurements of sequence to be uncovered, but do not yet measure explicit sequence distributions. One of the most useful methods to measure sequence information is nuclear magnetic resonance (NMR) spectroscopy, which can be used to measure fragments such as dyads and triads. In addition, the chemical composition distribution (CCD), which can be the fingerprint of the sequence, can be measured using MALDI‐ToF‐MS .…”