Studies on the interpolymer complex formation between poly(methacrylic acid) and poly(L-roline) with various conformations

Abstract

Interpolymer complex formation between PLP with helical structure and PMAA with random coil structure through hydrogen bonding has been studied by several experimental techniques e.g., viscosity, turbidity, and pH measurements. The change of pH as a function of time shows that the interpolymer complex formation follows the second order reaction first and then deviating toward first order in the final stage of reaction. It is consistent with the general pathway of interpolymer complex formation, i.e., nucleation followed by chain growing. The viscosity, turbidity, and pH experiments show that the left-handed helix of PLP (Form II) forms complex with PMAA faster than the right-handed helix of PLP (Form I). The expectation of the high ability of the left-handed helix of PLP from the geometrical and structural point of view is agreeable to the experimental results. From the turbidity and pH measurements, unexpected results were found out such as the high ability of complexation at intermediate PLP conformer ($\theta=45$) which coexists trans-cis monomers equally and the pH fluctuation deviating from the regular trend. The high ability of complexation at intermediate PLP conformer ($\theta=45$) may be caused by the high flexibility of the intermaediate PLP conformer since several kink in helix may make the helix flexible and partly disordered state. The pH fluctuation showed the irregular feature corresponding to the trans fraction of PLP. It may be the result of reversible process between intermediate steps. The existence of kink and the mechanism of complexation must be investigated further.