Influence of intrachain interactions on the kinetics of styrene polymerization and copolymerization

Abstract

SynopsisIn the free-radical polymerization of styrene, it has been observed that the onset of an acceleration of the polymerization due to increased solution viscosity can be quantitatively measured as occurring at a critical point. The product of the degree of polymerization of the polymer in solution at the critical point times its volume fraction can be represented by a temperature-dependent constant (P,V, = K ) . The value of the constant passes through a maximum between 60 and 90°C. The value of the constant is somewhat lower than that for the phenomenon called chain entanglement. It is postulated that the temperature-dependent behavior of K is due to a previously reported solution phase transition which is believed to be caused by interaction between phenyl groups on the polystyrene chain. Observations on the ultraviolet absorbance of styrene copolymers and calculations on the absolute rate of copolymerization of styrene with methyl methacrylate are presented to support the postulated intrachain interactions.

Detailed copolymer characterization using ultraviolet spectroscopy

“…In the case of copolymers and other complex polymers, the spectra (E,,,) which correspond to some of the species present can be obtained directly from the homopolymers of the monomers used to synthesize the polymer. If there are no effects on the absorption behaviour due to inter-and intramolecular interactions between the functionalities present in the solvent and in the polymer molecule, the direct application of [2] or [3] together with the spectra of the homopolymers and the initiator fragments should yield the copolymer composition estimates. However, if interactions are present, as in the case of styrene copolymerized with polar comonomers (4), the spectra of the chromophores present may be altered in an, as yet unknown, fashion.…”

“…These deviations have been attributed to the microstructure of the polymer chains (3,4,8,10, I I) and in some cases to the conformation of the molecules in solution (2, 6, 9). Vala and Rice (2) observed that the extinction coefficient of isotactic polystyrene at certain wavelengths is smaller than the corresponding extinction coefficients for atactic polystyrene.…”

“…Hypochromic effects on styrene copolymers were first reported by O'Driscoll et ul. (3) from observations made in the analysis of styrene -methyl methacrylate copolymers (SMMA). These authors suggested that the differences in the extinction coefficients were due to differences in the length of the styrene sequences present in the polymer chains.…”

“…The solution to the nontwo similar chromophores, butylbenzene and its stereoisomer, linear eq. [2] or [3] for N i parameters can be accomplished tert-butylbenzene (Figs. I and 2), indicates the importance of using any of the nonlinear least-squares estimation techniques steric effects in modifying the absorption pattern of a single (16).…”

“…Band shifts, solvent effects, and hypochromic effects have been observed as functions of the copolymer composition and the microstructure of the polymer chains (2)(3)(4)(5)(6)(7)(8). The band shifts, solvent effects, and other anomalies observed in the absorption behaviour of polymers have precluded the development of analytical techniques which can yield composition estimates directly from the uv spectra (4).…”