Search

Abstract: Amorphous hybrid materials with participation of water soluble biopolymer (pectin from apple-AP) and silica derived from tetraethoxy silane (TEOS) were synthesized by sol–gel method. The influence of biopolymer content was determined. The principles of the hybrids formation were developed using structural data from Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Differential thermal analysis (DTA/TG), and 13C-Nuclear magnetic resonance (13C-NMR) analysis. The most probable model of interaction between pectin and silica network in the hybrid materials were proposed. It has been found that the reaction between the organic and the inorganic components was performed by depolymerization of the intermolecular H-bonds. The formation of new H-bonds between silica and pectin was supposed.Graphical abstract: [ABSTRACT FROM AUTHOR]

Using carbon dioxide as feedstock for polymers is a big challenge and a chance for our sustainable future. It has an immense potential for the coming decade, which comes much faster than expected. Scientists are very active lately in carbon dioxide chemistry research, especially in the field of carbon dioxide based chemicals and polymers. We report here on the stability of higher molecular weight polycarbonate diols and the formation of specialty polyurethanes such as UV stable elastomers, semi-rigid foams, and elastic sealants. These polyurethanes are produced from polycarbonate diols (ETERNACOLL®) and aromatic 4,4'-diphenyl-methane diisocyanate, from aliphatic hexane-1,6-diisocyanate, or the trimer, diisocyanates. We use butane-1,4-diol or pentane-1,5-diol as a chain extender. The thermal and mechanical properties of the polyurethanes obtained are determined by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The data obtained show no phase segregation or any type of crystallinity. Any possible changes in the molecular mass distribution of the samples are investigated with the application of gel permeation chromatography (GPC). It is evidenced that only heat treatment brings about molecular mass distribution shifts to lower values. [ABSTRACT FROM AUTHOR]

Shape memory polyurethanes (SMPUs) based on recycled polyvinyl butyral and 4,4'-diphenylmethane diisocyanate, hexane-1,6-diol, and polypropylene glycol of varying hard segment content were investigated. Their mechanical properties and shape memory effect in particular were examined defining the amorphous soft segment domain as a reversible phase, while the crystalline hard segment domain as a frozen phase. Effects of hard segment content (30 - 45 %) and maximum strain on the cyclic tensile and mechanical properties below (25°C) and above (70°C) material glass transition temperatures were studied. The properties reversibility observed on repeated deformation was improved by decrease of the deformation magnitude and the increase of the hard segment content. [ABSTRACT FROM AUTHOR]

Shape memory polyurethanes (SMPUs) were synthesized by 4,4′-diphenylmethane diisocyanate (MDI), hexane-1,6-diol (HD), polypropylene glycol (PPG), and recycled polyvinyl butyral (PVB). Dynamic mechanical analysis, differential scanning calorimetry and Fourier transformation infrared attenuated total reflection spectroscopy was used to characterize the poly (vinylbutyral-urethanes). Micro-phase domain separation of hard and soft segments and phase inversion were investigated. Increasing the hard segment content, i.e., average hard segment molecular weight, leads to an increase in the degree of micro-phase separation, hard domain order and crystallinity. The crystalline hard segment structures combined with the elastic nature of soft segment matrix provide enough physical and chemical crosslinks to have shape memory effect. [ABSTRACT FROM AUTHOR]

Methylcellulose (MC) / SiO organic / inorganic hybrid materials have been prepared from MC and methyltriethoxysilane or ethyltrimethoxysilane, and characterized by XRD, FTIR and AFM. XRD showed peak shifts. FTIR shows intermolecular hydrogen bonding between MC and SiO. AFM depicts surface roughness which depends on the silica precursor and MC content. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]