Polymer, Vol.36, No.7, 1479-1486, 1995
Solvent Dependence of the Chain Flexibility, Aggregation and Gelation of Spin-Labeled Poly(Octyl Isocyanate)
A spin-labelled poly(octyl isocyanate) has been synthesized by copolymerizing a nitroxide radical having an isocyanate function, with n-octyl isocyanate. The electron paramagnetic resonance spectra of the labelled polymer in various solvents are sensitive to the local conformation and flexibility of the polyisocyanate chain. The motion of the label is less restricted in a polar solvent (chloroform) than in the non-polar hydrocarbons. Poly(octyl isocyanate) shows a tendency to form aggregates in certain solvents; in solvents with low polarity the aggregation leads to the gelation of the solution. A dipolar interaction between the nitroxide labels is observed in some of the samples. The proximity of the labels is suggested to be dependent not only on the solvent quality but also on the local ordering of the polymer chains.