Pablo S. Anbinder

Chitosan-graft-poly(n-butyl acrylate) copolymer: Synthesis and characterization of a natural/synthetic hybrid material.

Two chitosan polymers with different deacetylation degree and molecular weight were subjected to grafting reactions with the aim to enhance the properties of these bio-based materials. Specifically, n-butyl acrylate in different proportions was grafted onto two different deacetylation degree (DD%) chitosan using radical initiation in a surfactant free emulsion system. Infrared spectroscopy was used to confirm grafting and products grafting percentage and efficiency were evaluated against acrylate/chitosan ratio and DD%. Thermal and structural properties and the behavior against water of the raw and grafted biopolymers were studied using several experimental techniques: differential scanning calorimetry, transmission electron microscopy, dynamic light scattering, water swelling, contact angle and positron annihilation lifetime spectroscopy. The influence of the grafting process on the morphological and physicochemical properties of the prepared natural/synthetic hybrid materials is discussed.

Morphology and properties of neutralized chitosan-cellulose nanocrystals biocomposite films

Chitosan/cellulose nanocrystals (CH-CN) films were obtained by casting of dispersions, and treated with NaOH for neutralization proposes. The composition of films was varied from 1 to 10wt.% of CN. Changes in the morphology of the systems were correlated with the different properties studied. FTIR revealed the presence of a weak interaction between the polymer matrix and nanofiller, confirmed by a slightly increase in thermal stability. SEM images suggested that incorporating CN amounts higher than 3wt.% generates phase-segregated systems, and SAXS showed that CH avoid the typical organization of CN at concentrations below 5wt.%. Improved performance against water was obtained in composite materials comparing to the pure polymer matrix, as well as CH and CH-CN films did not show antibacterial activity demonstrating that remnant acetic acid, when no neutralization step is done, plays an important role in this property.

A Microstructural Study of Acrylic-Modified Chitosan by Means of PALS and SAXS

Chemical modification of chitosan, specially grafting with different polymers is an important strategy in the production of bio-based materials with enhanced properties. In the present study, chitosan was grafted with n-butyl acrylate, in a surfactant-free emulsion polymerization. Stable dispersions with high grafting efficiency were obtained and the microstructure of the casted films was analyzed by positron annihilation lifetime spectroscopy and small angle X-ray scattering. Results are discussed in terms of the number and distribution of the grafting sites.