Thermal stability of potato starch depends on amylose content. Temperature at 50% mass loss from thermogravimetric analysis was used to determine the starch components. The same analysis was carried ...out to analyse the samples from potato, rice, wheat and high amylose. The results (26.9% of amylose content for potato, 29.1% for rice and 20.9% for wheat) were compared with results obtained from the blue value method and enzymatic method. Satisfactory compatibility for potato and rice was obtained. For such kind of samples thermogravimetric analysis can be used for amylose determination.
Sponges are probably the earliest branching animals, and their fossil record dates back to the Precambrian. Identifying their skeletal structure and composition is thus a crucial step in improving ...our understanding of the early evolution of metazoans. Here, we present the discovery of 505-million-year-old chitin, found in exceptionally well preserved Vauxia gracilenta sponges from the Middle Cambrian Burgess Shale. Our new findings indicate that, given the right fossilization conditions, chitin is stable for much longer than previously suspected. The preservation of chitin in these fossils opens new avenues for research into other ancient fossil groups.
Polyelectrolytes such as poly(acrylic acid) and poly(allylamine hydrochloride) with opposite charges have been deposited on a polypropylene textiles by the layer-by-layer technique. The first acidic ...layer was produced by grafting of acrylic acid onto the surface according to the previously established procedure. The surface properties of the new materials have been studied by electrokinetic analysis. It has been found that there is a strict relationship between the type of polyelectrolyte layer deposited on a fabric surface and the electrokinetic properties of this fabric. Based on the results obtained, it can be concluded that the deposition of succeeding polyelectrolyte layers fails to provide a complete coverage of the modified surface. It has been also found that the result of zeta-potential measurement is not affected by the molecular weight of polyelectrolyte and the value of electrokinetic potential depends exclusively on the type of the top layer rather than on the substrate, on which the layer is deposited.
In this work the thermal properties of chitins of different origin were compared using a thermogravimetric technique. The α
s
-α
r
method, which makes possible a comparison of the thermal resistances ...of materials with similar thermostability, was used. The basic range of thermal conversion was determined. In this range, the thermal resistance depends on the chitin origin. The value of activation energy was calculated. No influence on the average molecular mass, crystallinity and the degree of acetylation on the thermal resistance was observed. On the other hand, it was found that the thermal stability depends on the size and perfection of crystallites as well as on the crystalline form of the chitin.
Electroactive polymers (EAPs) are functional materials that, stimulated by an electric field, change its composition or molecular structure so that the material expands, contracts, or bends (Guzmán ...et al. in J Appl Polymer Sci 112:3284–32931, 2009) and (Rappaport et al. in A glucose fuiel cell for implantable brain machine interfaces, Massachusetts Institute of Technology, Cambridge, 2012). The literature has shown that Chitin and Chitosan are considerably versatile and promising biomaterials to be used as EAPs in medical and biomedical applications as cochlear implant, and due to its chemical structure, is considered a biocompatible, bio-adhesive and biodegradable polymer (Falguni et al. in Proceedings of the 2010 IEEE Students Technology Simposium, IIT Kharagpur, 2010). Their amino and hydroxyl groups can be easily modified by organic (Younes et al. in Process Biochem 47:2032–2039, 2012) or cross-linked reactions, to obtain sophisticated functional medical devices (Wongpaint et al. in Micromol Biosci 5:1001–1012, 2005). This research collaboration aims to prove that Chitosan-based membranes could be synthetized as EAPs; as well as determine that there are useful ionic flow and movement responses on them. Chitosan-based membranes were prepared by the film-casting traditional method, treated with Tetraammineplatinum (II) chloride hydrate and Silver Nitrate by the ion exchange polymer method; and then cast with Sodium and Potassium Chloride as conductive salts. Membranes were tested at different voltages, as well as the chemical tests as FTIR, XRD, TGA and tensile strength and elongation as a function of the treatment applied. Film properties depended on its morphology, which is affected by Molecular Weight, degree of
N
-acetylation (DDA%), solvent evaporation and free amine regenerating mechanism (Younes et al. in Process Biochem 47:2032–2039, 2012) and (Wongpaint et al. in Micromol Biosci 5:1001–1012, 2005). Samples exhibited good displacement increasing as the applied voltage increased; best tip displacement was located as 17 mm at 7 V; and best theoretical δ value is found at 29.6 mm.
Well-defined comb polymers consisting of branched homo poly(ethyleneimine) (bPEI), or poly(ethyleneimine) with grafted poly(2-ethyl-2-oxazoline) (PEI-PEtOx), having varying degrees of polymerization ...(DPs) of the main chain and branches, have been successfully deposited onto a poly(propylene)
nonwoven textile fabric (PP) using a layer-by-layer technique. The surface properties of the materials have been studied by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Changes in the net surface charge and the electrostatic behaviour have been
studied by employing electrokinetic and electrostatic measurements. The deposition of the electrolytes increased the thermal stability of the nanomaterials and enabled the absorption of copper ions from solution.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Abstract
By Schotten-Bauman's esterification of starch with (meth)acryloyl chlorides, an ester derivative of starch - (meth)acryloyloxystarch - was prepared, which contains double bonds. The original ...starch and (meth)acryloyloxystarch were characterised by FTIR,
1
HNMR,
13
C-NMR, GPC and TGA. (Meth)acryloyloxystarch was polymerised in solution by the free-radical process and by photopolymerisation in a solid state to obtain a crosslinked product.
PDF
