Search results for "Chemical modification"

Oxazoline-containing compatibilizers for polyamide/SAN and polyamide/ABS blends

2002

Polyamide (PA) and acrylonitrile/butadiene/styrene copolymer (ABS) may appear as a mixture in the recycled plastic stream. The incompatibility of these blends results in a blend with poor mechanical properties. The aim of this work is to partially convert the nitrile groups of the acrylonitrile/styrene copolymer (SAN) into oxazoline groups by reaction with aminoethanol (AE). Such modified SAN (SAN-m) can react with the amine or carboxylic acid end groups of PA, and therefore used as compatibilizers for blends of PA with ABS. SAN-m was found to reduce the SAN-domain size in the PA/SAN-blends. The initial acrylonitrile content of SAN-m had a strong influence on the degree of conversion into o…

Carboranyl Substituted Siloxanes and Octasilsesquioxanes: Synthesis, Characterization, and Reactivity

2008

Carboranyl-containing disiloxane, cyclic-siloxane and cage-like silsesquioxane have been prepared in high yields. Two routes are compared for their preparation, a classical hydrolytic process based on hydrolysis and condensation of the freshly prepared carboranylalkylchlorosilane and ethoxysilane precursors and a nonhydrolytic route based on the specific reactivity of chorosilane toward DMSO. Based on the typical reactivity of the carboranyl group toward nucleophiles, dianionic disiloxanes and octaanionic silsesquioxanes were obtained without modification of the siloxane bond. Products are fully characterized by FTIR, NMR and MALDI-TOF methods.

Partially Quarternized Amino Functional Poly(methacrylate) Terpolymers: Versatile Drug Permeability Modifiers

2011

Partially quarternized poly(methacrylate) terpolymers (Q-BBMCs) have been synthesized, based on the basic butylated methacrylate copolymer (BBMC/EUDRAGIT E), an excipient approved by the Food and Drug Administration (FDA) and to date mainly applied for tablet coatings. Via straightforward polymer modification reactions, a series of Q-BBMCs with quarternization degrees of 22%, 42%, and 65% has been prepared. Apical to basolateral transport across Caco-2 cell monolayers was investigated, employing the paracellular transported compounds trospium and mannitol. At pH 6.5 quarternization resulted in increased permeation enhancement up to 2.8-fold compared to BBMC, that is, up to 7.3-fold compared…

Modification of carboxyl groups of poly(ethylene-co-acrylic acid) via facile wet chemistry method: A kinetic study

2010

Abstract In this work, we present the results of a kinetic study of the surface modification of the carboxyl group of poly(ethylene-co-acrylic acid) into acyl chloride. Reaction temperature and time, concentration of the reactants, kind of agitation have been changed in order to understand their effect on the conversion. A study on the penetration of the reaction inside the sample bulk was also performed. The results indicate that, when short reaction times are adopted, the reaction limits to the outer layers of the samples and, in this case, on increasing the temperature, the concentration of the reactants and the stirring allows having a faster kinetic. At longer reaction times, the react…

Synthesis and Characterization of Poly(glyceryl glycerol) Block Copolymers

2008

HPMC-salicylate conjugates as macromolecular prodrugs: Design, characterization, and nano-rods formation

2009

The design, characterization, and nano-rods formation of hydroxypropylmethylcellulose (HPMC)-salicylate conjugates as macromolecular prodrugs, was described. HPMC, obtained from Zhejiang Zhongbao Imp and Exp Corp, was dried under vacuum at 110°C for 8 hr. Nanoparticles were prepared using dialysis process in which 170 mg of HPMC-salicylate sample was dissolved in 5 mL of purified DMSO and was dialyzed against distilled water for 4 days. HPMC-salicylic acid conjugates reveal the absence of sulfur in all of the samples showing that there is no introduction to tosylate groups either covalently bounded or as an impurity.

UV-photocrosslinking of inulin derivatives to produce hydrogels for drug delivery application.

2005

In this work, INU, a natural polysaccharide, has been chemically modified in order to obtain new photocrosslinkable derivatives. To reach this goal, INU has been derivatized with MA thus obtaining four samples (INU-MA derivatives) as a function of the temperature and time of reaction. An aqueous solution of the derivative INU-MA1 was irradiated by using a UV lamp with an emission range from 250 to 364 nm and without using photoinitiators. The obtained hydrogel showed a remarkable water affinity but it underwent a partial degradation in simulated gastric fluid. To overcome this drawback, INU-MA 1 was derivatized with SA thus obtaining the INU-MA1-SA derivative designed to produce a hydrogel …

(-)-Isosteviol as a Versatile Ex-Chiral-Pool Building Block for Organic Chemistry

2013

(–)-Isosteviol is readily available in large quantities by the acidic treatment of a common alternative sweetener. The two functional groups of (–)-isosteviol are presented on the same side of the ent-beyerane scaffold with a mutual C–C distance of about 7 A. Their unique concave arrangement experiences a strong asymmetric environment due to an adjacent methyl group. Consequently, this building block has found several applications in supramolecular chemistry and organocatalysis. These areas and the chemical modification of this scaffold as well as its biological activity are surveyed.

Utilisation of barium-modified analcime in sulphate removal: Isotherms, kinetics and thermodynamics studies

2017

Abstract Analcime and commercial zeolite were employed as a precursor for preparing sorbent material for SO42− removal over barium modification. Three sorbents were prepared: barium-modified analcime (ANA-Na-Ba), barium-modified acid-washed analcime (ANA-Ac-Na-Ba) and barium-modified zeolite (ZSM5-Na-Ba). Of the prepared materials, ANA-Ac-Na-Ba was the most efficient sorbent material for SO42− removal, with a maximum sorption uptake of 13.7 mg g−1 at room temperature. Batch sorption experiments were performed to evaluate the effect of initial pH, initial SO42− concentration, sorbent dosage, temperature and contact time of sorption. Several isotherms were applied to describe the experimental…

Synthesis of molecularly uniform model oligomers for 1,5-naphthalene diisocyanate and 1,4-butanediol based polyurethanes by using the 3,5-di-tert-but…

1997

A modified benzyloxycarbonyl (BOC) protective group, the 3,5-di-tert-butyl substituted BOC (3,5-tBBOC) group, was introduced to the stepwise synthesis of molecularly uniform oligourethanes based on 1,5-naphthalene diisocyanate (NDI) and 1,4-butanediol (BDO) for the protection of the amino functions of the starting material 1,5-naphthalene-diamine (NDA). The tert-butyl substituents of the 3,5-tBBOC group significantly improved the solubility of the intermediate products in the oligourethane synthesis. Thus, applying this modified protective group, reactions could be carried out, which were not possible with the conventional BOC group, due to the insolubility of the compounds in all suitable …