Low and medium molecular weight copolymers constituted by glycolide and p-dioxanone units have been synthesized by a ring-opening polymerization. The p-dioxanone monomer was obtained from ...(2-hydroxyethoxy)acetate or by thermal depolymerization of poly(p-dioxanone). ¹H and ¹³C NMR spectra were highly sensitive to the chemical sequences, which were effectively assigned by considering the data from samples with different compositions, and the acquisition of heteronuclear ¹H and ¹³C NMR-correlated spectra. End groups were also identified, allowing methylene protons of sequences involving up to two glycolide units to be distinguished. These data seem basic to analyze degradation products or the influence of thermal treatments in chain microstructure. Glycolide/p-dioxanone copolymers are an interesting system because changes on chemical sequences can easily occur due to a depolymerization reaction that eliminates p-dioxanone residues. Furthermore, depending on the polymerization conditions, the occurrence of transesterification reactions may be highly significant. These reactions have a great impact in properties such as the melting temperature and can be easily quantified by NMR spectroscopy because of the occurrence of a new chemical sequence.
Metal-free catalysis was successfully applied to polymerize ¿-pentadecalactone (PDL) by ring-opening polymerization (ROP) using several amino-ended initiators, namely hexylamine, allylamine and ...O,O'-bis(3-aminopropyl)diethylene glycol. This polymerization method was suitable to prepare telechelic polyesters carrying functional-end groups. The technique was then extended to the synthesis of block copolymers by ROP of PDL using bisamino-ended poly(ethylene glycol) (Mn¿=¿2600) as macroinitiator. PPDLx-PEG56-PPDLx triblock copolymers with Mn ranging between ~4000 and ~90,000¿g¿·mol-1 were synthesized and extensively characterized by NMR, DSC, TGA and XRD. The amphiphilic copolymers thus produced were demonstrated to be able to self-assemble in nanoparticles with average diameters of ~100–200¿nm and morphologies highly depending on blocks lengths. The described synthetic route distinguishes in providing “clean” amphiphilic copolymers, which are attractive candidates for biomedical applications.
Peer Reviewed
Dyeing is supercritical CO2 is one of the most advanced dyeing technologies. The dyeing medium is not water but carbon dioxide in the supercritical state (temperatures above 31°C and pressures above ...74 bar).
The effect of pressure and temperature on dyeing of PET in supercritical CO
2
with only one dye and with mixtures of two or three dyes has been investigated.
The variations of pressure (250 in 300 bar) and temperature (70 in 130°C) cause differences in colour, especially when mixtures of dyes are used. The dyed samples were evaluated using colorimetry and the extraction of dyes from the fabric.
The amount of all dyes on the fabric rises with the rising temperature due to the accelerated motion of molecular chains and the formation of the free volume in the fibre, so important for the diffusion of dyes. The change of pressure does not after the amount of fixed dyes significantly, but the ratio between the dyes is changed when dyeing with mixtures of dyes.
The weight of textile components in automobiles is expected to rise to 35 kg by 2020, and the average lifetime of a vehicle is about 12 years. Car seats are the most important part of the interior ...decoration, and polyester is the most widely used material in car seat covering. Abrasion resistance tests are used to quantify the duration of car seat upholstery in normal usage, and this is one of the most important requirements. Several testing methods, standards, and car producer specifications have been developed to define the abrasion resistance of specified materials, and pre-tests have been taken to identify parameters for this research. The objective of this study was to compare three abrasion tests with different abrasive elements using car seat upholstery structures. Comparison among abrasion testers and abrasive papers shows statistically significant differences. The relationship between weight loss and abrasion cycles can be modelled by regression equations
Poly(ester amide)s are an emerging group of biodegradable polymers that may cover both commodity and speciality applications. These polymers have ester and amide groups on their chemical structure ...which are of a degradable character and provide good thermal and mechanical properties. In this sense, the strong hydrogen‑bonding interactions between amide groups may counter some typical weaknesses of aliphatic polyesters like for example poly(e-caprolactone). Poly(ester amide)s can be prepared from different monomers and following different synthetic methodologies which lead to polymers with random, blocky and ordered microstructures. Properties like hydrophilic/hydrophobic ratio and biodegradability can easily be tuned. During the last decade a great effort has been made to get functionalized poly(ester amide)s by incorporation of a-amino acids with hydroxyl, carboxyl and amine pendant groups and also by incorporation of carbon-carbon double bonds in both the polymer main chain and the side groups. Specific applications of these materials in the biomedical field are just being developed and are reviewed in this work (e.g., controlled drug delivery systems, hydrogels, tissue engineering and other uses like adhesives and smart materials) together with the main families of functionalized poly(ester amide)s that have been developed to date.
Peer Reviewed
Synthesis and purification of sucrose polyesters (SPE) were optimized to obtain high yields of SPE. Sucrose octaacetate (SOAC) and fatty acid methyl esters (FAME) of salad oils or FAME blends of ...homogenous fatty acids and salad oils were interesterified in the presence of sodium metal. Yields 99.6-99.8% of purified SPE based on initial weight of SOAC were obtained. SPE structure was confirmed by infrared (IR) and C-13 nuclear magnetic resonance (C-13 NMR) spectroscopy. Physical properties of SPE and raffinose polyesters (RPE) were similar to physical properties of conventional salad oils. The hydrophile-lipophile balance (HLB) of SPE and RPE were between 2-6 HLB units. Differential scanning calorimetry (DSC) was used to determine the melting properties of SPE and RPE. Neither SPE nor RPE was susceptible to in vitro lipolysis.
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