Polymer-polymer hydrogen-bonded complexes of poly(monomethyl itaconate
) with poly(2-vinylpyridine) and poly(4-vinylpyridine) were studied. S
everal solvents have been assayed for these systems: methanol, methylf
ormamide and binary mixtures (50/50) of methanol with water, tetrahydr
ofuran, dimethylformamide and dimethylacetamide. In all cases, instant
aneous precipitate formation was observed after mixing the solutions o
f poly(monomethyl itaconate) and poly(vinylpyridine)s. Polymer complex
es prepared from methanol solutions show different stoichiometries dep
ending on the feed composition, but that found in most cases was 3:2 o
f monomethyl itaconate:vinylpyridine repeat units. Complexes are insol
uble in all the tested solvents; only fresh precipitate may be solubil
ized by increasing the pH of the solution. Complex formation is observ
ed even when the density of pyridine groups is reduced to 25% by copol
ymerization with styrene. Differential scanning calorimetry analyses d
o not show a glass transition temperature for poly(monomethyl itaconat
e) polymer complexes; only a wide degradation peak was observed. Therm
ogravimetric experiments corroborate that the thermal degradation beha
viour does not differ substantially from that of the pure components.
In these conditions, Fourier-transform infra-red spectroscopy was used
to study their hydrogen-bonding interactions. The infra-red spectra c
orresponding to polycomplexes clearly show evidence of hydrogen bondin
g between the components and there seems to be some evidence of partia
l pyridine protonation.