Microstructural characterization of a natural/synthetic hybrid material by means of PALS and SAXS

MACCHI, CARLOS; AMALVY, JAVIER; ANBINDER, PABLO; SOMOZA, ALBERTO

Campinas

Encuentro; 26th RAU - Annual Users Meeting LNLS/CNPEM; 2016

Laboratorio Nacional de Luz Sincrotrón - Centro Nacional de Pesquisa em Materiales e Energía

Chitosan is a biopolymer which offer great potentiality as packaging material, due to its inherentantimicrobial activity, non-toxicity and biodegradability [1,2]. Chemical modification of chitosan,specially grafting with different polymers is an important topic in the production of bio-basedmaterials with enhanced properties. In the present study, two chitosan with different deacetylationdegree (DD%) and molecular weight were grafted with different proportions of n-butyl acrylate, in asurfactant-free emulsion system. Stable dispersions with high grafting efficiency were obtained andthe microstructure of the dispersions and casted films was analyzed by small angle x-ray scattering(SAXS) and positron annihilation lifetime spectroscopy (PALS). Results were studied and comparedtaking into account the DD%, molecular weight and grafting ratio.A core-shell structure was obtained on grafted samples dispersions and, on the other hand, a ruptureof the typical rigid rod-structure of the polysaccharides was evidenced in hybrid films. Grafted polybutylacrylatechains break specific interactions in chitosan matrix, increasing the free nanoholevolume and their fraction.Differences in DD% and molecular weight in pristine chitosan play an important role in graftedsamples microstructure because of the number and distribution of graft sites.