Sanja Šešlija

Cross-linking of highly methoxylated pectin with copper: the specific anion influence

The aim of this work was to investigate the influence of specific anions on the cross-linking process of highly methoxylated pectin using the following copper salts CuSO4; Cu(C2H3O2)2; CuCl2; and Cu(NO3)2 wherein the initial salt concentrations were varied from 0.5 up to 10 g l−1. It was found that the anions affected the sorption capacity wherein the Cu2+ sorption capacity from the sulphate solution was the highest, while it decreased in the presence of CH3COO−, Cl− and NO3− ions, respectively. This difference was mostly pronounced at the higher initial salt concentrations (c0(Cu2+) > 2 g l−1). The obtained beads were characterized by FTIR, AAS, SEM/EDS microanalysis and mechanical compression tests up to 80% of deformation. The sorption data were applied to the Langmuir and Freundlich isotherm models and various calculated parameters confirmed the sulphate anion supportive nature in metal ion binding. The value of the Kf parameter for the cross-linking process of pectin in the presence of acetate, chloride and nitrate was approximately the same (Kf ≈ 0.027 g g−1), while it was higher in the presence of sulphate anions by more than 20% (Kf = 0.0352 g g−1). The predicted 1/n values (1/n 1, 1/n = 1 for the sulphate, nitrate and acetate, and chloride anions, respectively) were the quantitative confirmation of the specific interactions involved in the cross-linking mechanism caused by different anions. The established anion influence was in accordance with the typical ion-specific influence on macromolecules in aqueous systems proposed by Hofmeister.

Simple One-Pot Synthesis of Fully Biobased Unsaturated Polyester Resins Based on Itaconic Acid

For the preparation of fully biobased unsaturated polyester resins (UPRs), the replacement of styrene with alternate nonpetroleum-based monomers turned out to be one of the most challenging tasks. Its complexity lies in the fact that reactive diluents (RD) have to have low viscosity and volatility, good compatibility with prepolymer, and capability to homopolymerize and copolymerize with its unsaturations. In this context, we directed our efforts to develop fully biobased UPRs using the dialkyl itaconates as an alternative to styrene. Therefore, a series of 100% biobased UPRs were prepared from itaconic acid and 1,2-propandiol and diluted by dialkyl itaconates. The resins were characterized by Fourier transform infrared spectroscopy, NMR, volatility, and viscosity measurements, while the cured samples were characterized by dynamic mechanical properties, thermomechanical analysis, thermogravimetric analysis data, and tensile tests. The influence of RD structure on the properties of cured samples was discussed in detail. It was shown that the prepared resins had evaporation rates of dialkyl itaconates of several orders of magnitude less compared to styrene. The cured resins with dimethyl itaconate showed comparable or even better thermal and mechanical properties compared to the one with styrene. This investigation showed that itaconic acid and dialkyl itaconates are promising bioresources for the preparation of fully biobased UPRs for mass consumption.

The Mechanical Properties of a Poly(methyl methacrylate) Denture Base Material Modified with Dimethyl Itaconate and Di-n-butyl Itaconate

This study investigates a wide range of clinically relevant mechanical properties of poly(methyl methacrylate) (PMMA) denture base materials modified with di-methyl itaconate (DMI) and di-n-butyl itaconate (DBI) in order to compare them to a commercial PMMA denture base material. The commercial denture base formulation was modified with DMI and DBI by replacing up to 10 wt% of methyl methacrylate (MMA) monomer. The specimens were prepared by standard bath curing process. The influence of the itaconate content on hardness, impact strength, tensile, and thermal and dynamic mechanical properties was investigated. It is found that the addition of di-n-alkyl itaconates gives homogenous blends that show decreased glass transition temperature, as well as decrease in storage modulus, ultimate tensile strength, and impact fracture resistance with increase in the itaconate content. The mean values of surface hardness show no significant change with the addition of itaconates. The magnitude of the measured values indicates that the poly(methyl methacrylate) (PMMA) denture base material modified with itaconates could be developed into a less toxic, more environmentally and patient friendly product than commercial pure PMMA denture base material.

Poly(methyl methacrylate) denture base materials modified with ditetrahydrofurfuryl itaconate: Significant applicative properties

The aim of this work was to examine the possibility of modification of commercial denture base materials with itaconic acid esters, in order to obtain materials with lower toxicity and higher biocompatibility. Despite their relatively higher price compared to methacrylates, itaconic acid and itaconates are materials of choice for environmentally friendly applications, because they are not produced from petrochemical sources, but from plant products. A commercial system based on poly(methyl methacrylate) was modified using ditetrahydrofurfuryl itaconate (DTHFI), whereby the ratio of DTHFI was varied from 2.5 to 10 % by weight. Copolymerization was confirmed using FTIR spectroscopy, while SEM analysis showed the absence of micro defects and pores in the structure. The effects of the itaconate content on the absorption of fluids, the residual monomer content, thermal, dynamic-mechanical and mechanical properties (hardness, toughness, stress and elongation at break) were investigated. It was found that the addition of DTHFI significantly reduced the amount of residual methyl methacrylate, which made these materials less toxic. It was shown that increasing the DTHFI content resulted in materials with decreased glass transition temperatures, as well as with decreased storage mod ulus, ultimate tensile strength and impact fracture resistance; however the mech anical properties were in the rang prescribed by ADA standards, and the materials could be used in practice. The deterioration in mechanical properties was therefore worthwhile in order to gain lower toxicity of the leached monomer.

Physico-chemical evaluation of hydrophobically modified pectin derivatives: Step toward application

Abstract Present study reports synthesis and physico-chemical evaluation of hydrophobically modified pectin derivatives, obtained by reacting of pectin with di-acyl chlorides (glutaryl and sebacoyl chloride). Depending on length of the inserted carbon chains, the acylation resulted in possible formation of mono-grafted (isolated chains) and bi-grafted (chemical gels) structures. The structural features of obtained derivatives were investigated using FTIR spectroscopy, confirming the successful synthesis. The concentrated aqueous solutions of modified pectin showed interesting rheological properties, having lower values of apparent viscosity compared to neat pectin. Since the GPC analysis indicated that no degradation occurred, the viscosity decrease was explained by more heterogeneous organization within modified pectin solutions (microparticles together with sticky polymer entanglement). A shift in particle size distribution proved that proposed modifications also affected pectin solution properties in diluted regime. The modified samples turned to be more sensible to thermal degradation than neat pectin, whereby the increasing size of flexible acyl chains attached to a polymer backbone reduced the glass transition temperature. The hydrophobicity of obtained derivatives was evaluated by sessile drop and du Nouy ring methods. It was found that acylation enhanced hydrophobicity of the pectin molecule, while hydrophobically associative character turned to be inconsistent in aqueous and non-aqueous environment.

The influence of nanofillers on physical–chemical properties of polysaccharide-based film intended for food packaging

Abstract Food packaging is an important part of the food industry wherein preservation and protection of all types of foods and their raw materials presents an imperative. Depending on water activity and temperature of storage, food material can be easily perishable and therefore needs appropriate protection against external influences in order to preserve it longer. Petrochemical based materials such as polyolefins, polyesters, and polyamides have been increasingly used as packaging materials, because of their availability in large quantities at low cost and satisfying functional characteristics. Despite all the advantages, these materials are totally nonbiodegradable and cause the problems in waste disposal. Therefore, the demands of the consumers have been shifted to ecofriendly biodegradable and biobased materials, obtained from renewable resources. Nonetheless, the usage of biopolymers has been limited due to the poor mechanical and barrier properties. The addition of nanofillers significantly improves the barrier, mechanical, and thermal properties of biobased materials, as well as petroleum-based materials. This chapter provides a review of implementation potentials and development of the nanocomposites materials based on polysaccharides (thermoplastic starch, chitosan, cellulose, alginate, pectin) in combination with various nanofillers with emphasis on mechanical, thermochemical, and barrier properties.