Synthesis of the triblock copolymers poly-γ-benzyl- l-glutamate-PMMA-poly-γ-benzyl- l-glutamate and study of their conformation in solution

Abstract

Using the polymeric initiator PMMA with terminal amino groups the authors have synthesized samples of the triblock copolymer of the ABA type, where A is poly-γ-benzyl- l-glutamate (PBG), B is PMMA. The synthesized polymer constitutes a coil of a flexible polymer to the ends of which are attached the helical sequences of PBG. The MM and the fraction of each component in the copolymer vary. Light scattering, flow birefringence and viscometry have been used to investigate solutions of the synthesized samples in DMFA at 25°C. The composition, MMs, intrinsic viscosities, the radii of inertia, the second varial coefficients and optical anisotropy of the copolymers and their components have been determined. A comparative analysis is made of the dependence of the intrinsic viscosity and optical anisotropy on the molecular mass for the copolymers and PBG homopolymer studied. It is shown that the introduction of a flexible long PMMA spacer into the rigid PBG macromolecule does not change its equilibrium rigidity. A model of the structure of the PBG-PMMA-PBG triblock copolymer is proposed helping to explain the body of experimental data.