Morphology of the poly(vinyl alcohol)–poly(vinyl acetate) copolymer in macrodefect-free composites: a 13C magic-angle-spinning nuclear magnetic resonance and 1H spin-diffusion study

A study was made of the macrodefect-free (MDF) composite based on aluminate cement and a poly(vinyl alcohol)–poly(vinyl acetate) (PVAc) copolymer by ¹³C cross-polarization magic-angle-spinning nuclear magnetic resonance. The spectra were run on both the copolymer and the MDF composite in order to observe the atomic environments of the carbon nuclei. An analysis of the intramolecular hydrogen bonds showed a stronger modification in the sample containing CaAl₂O₄ (CA) than in that containing Ca₃Al₂O₆ (C₃A). From the spectra, it was seen that deacetylation had occurred, and that there was interaction between acetate groups and the calcium and aluminium ions. Proton relaxation times both in the laboratory frame, T ₁(H), and in the rotating frame, T1ρ(H), were exploited for the study of the dimension of the polymer matrix in MDF composites. An extended interphase was identified in the composite containing CA. A comparison with the behaviour of the composite based on silicates Ca₃SiO₅–PVAc highlights the better mixing of the phases in the MDF composites containing CA. This revised version was published online in November 2006 with corrections to the Cover Date.