Intermacromolecular complexes due to specific interactions. 12. Graft-like hydrogen bonding complexes based on pyridyl-containing polymers and end-functionalized polystyrene oligomers

Soluble graft-like complexes were obtained via hydrogen bonding interaction between poly(4-vinyl pyridine) (PVPy) or poly(butyl acrylate-co-4-vinyl pyridine) (BVPy) and mono-carboxy terminated polystyrene (MCPS). The hydrogen-bonding interaction was evidenced by C-13 NMR and FT-IR. In the blend solution, the grafting of MCPS onto PVPy or BVPy backbones led to graft-like complexes showing much larger average hydrodynamic radius [R-h] than is shown by either component alone, the conformation of PVPy backbone undergo chain extension due to the steric repulsion of grafted MCPS chains. Moreover, both viscometry and LLS showed a strong effect of molar mass of MCPS on grafting, e.g. the number of branches on each PVPy backbone decreased from 330 to 3 as the molar mass increased from 1.8k to 23.4k. Fluorescence measurements in the blend solutions supported these conclusions. The DSC results of PVPy/MCPS blends in bulk showed two-phase structures as the hydrogen bonding interaction existing between carboxyl end and PVPy is not enough to cause complete mixing. Besides, the thermal history greatly influenced the phase behavior of the blends as the hydrogen bonding is sensitive to temperature. For the blends containing MCPS and BVPy-34 with lower VPy content and much lower T-g, miscibility over the whole composition range was obtained. (C) 2000 Elsevier Science Ltd. All rights reserved.