Preface for papers presented at AMSALS 2012

Preface for papers presentedat AMSALS 2012

Natural polymers and bio-inspired macromolecular materials

Growing societal awareness of environmental issues has become a driver to promote the design and production of polymeric products based on renewable or biological materials, as we outlined in the preface of the special issues of European Polymer Journal related to previous BiPoCo (Bio-based Polymers and Composites) conferences [1,2]. The BiPoCo 2016 Conference focused on the synthesis, characterization and degradation of biopolymers, the development of biocomposites and included topics on smart, nano-structured systems for controlled molecular release. We placed particular emphasis on issues about biocompatibility, biofunctionality and biodegradability of polymeric materials. Similarly to the previous two conferences, European Polymer Journal is publishing a selection of papers related to the meeting and this special section contains three feature articles and several original research papers with topics on nanoparticulate drug delivery, cell-material interaction, as well as synthesis and modification of biopolymers and hydrogels

Preparation of pH-Responsive Poly(aspartic acid) Nanogels in Inverse Emulsion

Poly(aspartic acid) (PASP) hydrogels were prepared by cross-linking polysuccinimide (PSI) with diaminobutane followed by the mild hydrolysis of the resultant PSI gels to PASP hydrogels. The composition dependence of the gelation time and the stiffness of bulk PASP hydrogels were determined by rheometry and compression tests, respectively. The composition of the prepared PASP nanogels was chosen based on the results on bulk PASP hydrogels. Prior to nanogel preparation stability of DMSO-in-oil (inverse) emulsions was tested as a function of the chemical quality of apolar phase, the concentration of the precursor polymer and the concentration of the surfactant. PASP nanogels in the size of a few hundred nanometers were prepared by the hydrolysis of PSI nanogels synthesized in inverse emulsion. PASP nanogels showed pH-dependent swelling and strongly negative surface charge at physiological pH values, thus they can be further developed to meet the specific criteria of different bio-related applications

A colourimetric method for the determination of the degree of chemical cross-linking in aspartic acid-based polymer gels.

A 2,4,6-trinitrobenzenesulphonic acid (TNBS)-based assay is developed to determine the degree of chemical cross-linking in aspartic acid-based polymer gels. The conventional colourimetric method for the quantitative determination of amine groups is difficult to use in polymer networks; thus, an improved method is developed to analyse polymer gels swollen in dimethyl sulfoxide (DMSO). Reaction products of the derivatizing reaction are examined by NMR. The chemical stability of the reagent is increased in DMSO, and the method shows satisfactory linearity and accuracy. The degree of chemical cross-linking in the investigated gels is close to its theoretical maximum, but the conversion of the pendant amine groups to cross-linking points is strongly dependent on the feed composition of the gels

Electrospun Nanofibers for Entrapment of Biomolecules

This chapter focuses on nanofiber fabrication by electrospinning techniques for the effective immobilization of biomolecules (such as enzymes or active pharmaceutical ingredients—APIs). In this chapter, the development of precursor materials (from commercial polymer systems to systematically designed biopolymers), entrapment protocols, and precursor-nanofiber characterization methods are represented. The entrapment ability of poly(vinyl alcohol) and systematically modified polyaspartamide nanofibers was investigated for immobilization of two different lipases (from Candida antarctica and Pseudomonas fluorescens) and for formulation of the antibacterial and antiviral agent, rifampicin. The encapsulated biomolecules in electrospun polymer fibers could be promising nanomaterials for industrial biocatalysis to produce chiral compound or in the development of smart drug delivery systems

The role of solubility and critical temperatures for the efficiency of sorbitol clarifiers in polypropylene

The optical properties of polypropylene (PP) were modified by nine different sorbitol type clarifiers available commercially or synthesized in the study. The solubility of the clarifiers in PP was estimated by thermodynamic model calculations. The results showed that the solubility of these additives in PP is small, a few 1000 ppm at most. Solubility is determined by the chemical structure of the sorbitol and the heat of fusion of the latter changes solubility by at least one order of magnitude. Solubility can be estimated reasonably by the Flory-Huggins lattice theory. The morphology of most sorbitols transforms at a temperature much below their melting point upon heating. This transformation, which is accompanied by crystal perfection, seems to influence melting and solubility. A fibrillar structure forms upon the cooling of molten sorbitols, but the diameter of the fibrils is much larger than those forming in the polymer melt. The nucleating effect of the clarifier depends on solubility, but also on processing conditions. Nucleus density is related to the amount of dissolved clarifier. A close correlation was found between the Flory-Huggins interaction parameter of sorbitols and the minimum achievable haze, which can be explained with the effect of solubility and nucleus density