Thermoplastic polyurethanes containing poly(dimethylsiloxane): Synthesis, properties and biocompatibility

Thermoplastic polyurethane (TPU) materials containing poly(dimethylsiloxane) (PDMS) segments have been used in various medical devices, primarily because of their good mechanical properties and biostability. However, PDMS-based TPUs, currently utilized for biomedical applications, have sub-optimal biocompatibility in terms of resistance to cell adhesion and relatively poor support for endothelial cell growth, which diminishes their efficacy. In order to significantly improve and extend clinical applications of PDMS-based TPUs, the aim of the research was to enhance the endothelial cell attachment and blood-contacting properties of these materials [1,2]. This study is focused on overview of the synthesis, characterization of the structure, surface, thermal, and mechanical properties, as well as investigation of biocompatibility of PDMS-based TPUs. The synthesized PDMS based TPUs exhibit good surface and thermo-mechanical properties, as well as good biocompatibility equal to current commercial biomedical TPUs

Synthesis and structure-property relationships of biodegradable polyurethanes

This chapter deals with a commercially very important part of the polyurethane (PU) polymer family, biodegradable polyurethanes (BioPUs). PUs are multiblock copolymers composed of a high molecular weight macrodiol, called a soft segment, and a hard segment composed of a diisocyanate and a low molecular weight diol. As a result of the thermodynamic incompatibility of the hard and soft segments in PU copolymers the phenomenon of microphase separation occurs. Nowadays, it is generally accepted that the overall properties, as well as the biocompatibility, of segmented PU and poly(urethane urea) (PUU) copolymers are correlated to the degree of microphase separation. The thermoplastic and elastic behaviour of these copolymers can be explained by their multiphase structure. The elastomeric properties of these copolymers are generally attributed to the phase separation of the hard and soft segments; the hard domains serve as crosslinks and reinforcing fillers in the matrix of the soft segment. It is generally assumed that the soft phase is responsible for the reversible elasticity of the polymeric material, whereas the hard phase is responsible for the mechanical strength properties

Synthesis and characteriaztion of polyurethanes cross-linked with aliphatic hyperbranched polyester

Two series of cross-linked polyurethanes (PUs) based on hydroxyethoxy propyl terminated poly(dimethylsiloxane) (EO-PDMS) or hydroxyl propyl terminated poly(dimethylsiloxane) (HP-PDMS) macrodiols, Boltorn® aliphatic hyperbanched polyester of the second pseudo generation (BH-20) and 4,4’-methylenediphenyl diisocyanate (MDI) were synthesized using two-step polymerization in solution. The influence of the type and content of soft PDMS segment on swelling behavior and thermal properties of PUs was investigated. The obtained results revealed that cross-linking density decreases, while thermal stability increases with increasing soft segment content. Furthermore, PUs based on EO-PDMS have higher cross-linking density and better thermal stability than samples synthesized using HPPDMS

Reološko ponašanje termoplastičnih poli(estar-siloksana)

Two series of thermoplastic elastomers (TPES), based on poly(dimethylsiloxane) (PDMS) as the soft segment and poly(butylene terephthalate) (PBT) as the hard segment, were analyzed by dynamic mechanical spectroscopy. In the first TPES series the lengths of both hard and soft segments were varied while the mass ratio of the hard to soft segments was nearly constant (about 60 mass%). In the second series, the mass ratio of hard and soft segments was varied in the range from 60/40 to 40/60, with a constant length of soft PDMS segments. The influence of the structure and composition of TPESs on the rheological properties, such as complex dynamic viscosity, μ*, the storage, G', and loss, G', shear modulus as well as the microphase separation transition temperature, TMST, was examined. The obtained results showed that the storage modulus of the TPESs increased in a rubbery plateau region with increase in degree of crystallinity. The rheological measurements of TPESs also showed that a microphase reorganization occurred during the melting process. The microphase separation transition temperatures were in the range from 220 to 234°C. In the isotropic molten state, the complex dynamic viscosity increased with increasing both the content and length of hard PBT segments.Dve serije termoplastičnih elastomera (TPES) na bazi poli(dimetilsiloksana) kao mekog segmenta i poli(butilentereftalata) kao tvrdog segmenta su analizirane dinamičko-mehaničkom spektroskopijom. U prvoj TPES seriji varirane su dužine tvrdih i mekih segmenata dok je njihov maseni odnos bio skoro konstantan (oko 60 mas%). U drugoj seriji, odnos tvrdih i mekih segmenata je variran u opsegu od 60/40 do 40/60, dok je dužina mekih PDMS segmenata bila konstantna. Ispitan je uticaj strukture i sastava TPES kopolimera na reološka svojstva, kao što su kompleksni dinamički viskozitet, μ*, moduli sačuvane, G', i izgubljene energije, G', i temperatura mikrofaznog razdvajanja, TMST. Dobijeni rezultati su pokazali da su uzorci sa većim stepenom kristaliničnosti imali i veće module sačuvane energije u gumolikom platou. Reološka merenja su takođe pokazala da svi TPES uzorci ispoljavaju mikrofaznu reorganizaciju u procesu topljenja. Temperature mikrofaznog razdvajanja su bile u opsegu od 220 do 234°C. U izotropskom rastopu, kompleksni dinamički viskoziteti su rasli sa povećanjem sadržaja i dužine PBT segmenata

Optimizacija uslova za degradaciju pesticida pomocu hlor dioksida

The аim of this study was to find optimal conditions for degradation of pesticides, such as pethoxamid and metazachlor with chlorine dioxide in deionized water.Cilj ovog rada је bio da se pronadju optimalni uslovi za degradaciju pesticida, kao sto su: petoksamid i metazahlor роmоću hlor dioksida u dejonizovanoj vodi

Degradation of triazine group herbicides by chlorine dioxide

This study investigates degradation of triazine group herbicides (atrazine, terbuthylazine and prometryn) with chlorine dioxide in deionized water and in real water system (water from river Sava) under optimal conditions

Characterization of polyurethane crosslinked structures based on hyperbranched polyester

The novel polyurethane crosslinked structures based on α,ω-dihydroxy-(ethylene oxide-poly(dimethylsiloxane)-ethylene oxide) (EO-PDMS-EO), 4,4’- methylenediphenyl diisocyanate and Boltorn® hyperbranched polyester of the second pseudo generation were characterized by infrared spectroscopy, scanning electron microscopy and thermogravimetric analysis. The chemical structure and hydrogen-bond interactions of these polymers were investigated by infrared spectroscopy. The carbonyl region was fitted by the Gaussian deconvolution technique, using the PeakFit program, resulting in the determination of locations and areas of each band. The polyurethanes exhibited five absorbance peaks in carbonyl region: hydrogen-bonded carbonyl groups in ordered hard domains at 1690 cm-1, free (non-bonded) carbonyl groups at 1735 cm-1, hydrogen-bonded carbonyl groups in disordered domains at 1715 cm-1, free carbonyl groups from ester bonds at 1725 cm-1 and hydrogen-bonded carbonyl groups from ester bonds at 1650 cm-1. The deconvolution procedure showed very good agreement between observed and generated values. The fit standard error was in the range from 0.00013 to 0.0028 and r2 > 0.994. The hydrogen bonds formation between urethane groups and between urethane –NH and ester carbonyl groups in polyurethanes increases with the decrease of EO-PDMS-EO content. The EDX analyses, performed to indentify the nature of the atoms present in the samples at a depth of 100-1000 nm from the surfaces, revealed the presence of all expected elements (C, O, Si and N). The Si percentage detected by EDX on the surface of polyurethanes increases with increasing PDMS content. The surface morphology of the polyurethanes indicated that the separation of the micro-domains was improved by increasing EO-PDMS-EO content. Thermal stability of polyurethanes increased with increase of EO-PDMS-EO content up to the temperature corresponding to the approximately 50 % of weight loss. However, at higher temperatures thermal degradation became slower for samples with lower EO-PDMS-EO content

Mechanical properties and morphology of the poly(urethane-siloxane) copolymers and their clay nanocomposites

In this paper the series of poly(urethane-siloxane) copolymers and their clay nanocomposites were synthesized based on 4,4'-diphenylmethane diisocyanate and 1,4-butanediol as the part of the hard segments (HS) and α,ω-dihydroxy-poly(propyleneoxide)-b-poly(dimethylsiloxane)-b-poly(propylene oxide) as the part of the soft segments (SS). Organomodified montmorillonite clay (Cloisite 30B®) was used as nanofiller in the amount of 1 wt.% within prepared nanocomposites. Mechanical properties and morphology of these polymers were investigated by dynamic mechanical thermal analysis (DMTA) and wide angle X-ray diffraction (XRD) measurements

Toxicity screening after degradation of organophosphorus pesticides with chlorine dioxide

Effectiveness, mineralization and toxicity of four organophosphorus pesticides (OPPs) azamethiphos (AZA), dimethoate (DM), fenitrothion (FEN) and malathion (MAL) in water with chlorine dioxide (ClO2) as degradation agent were investigated. Analyses included toxicity tests of parent pesticides and their degradation products (DPs), using Daphnia magna test organisms, and total organic carbon (TOC) analysis. Toxicity tests showed that all four pesticide DPs were less toxic than parent pesticides, but DM had higher toxic DPs compared to parent AZA, FEN and MAL. All DPs were classified as category III (on a scale from I to V) of toxicity as acutely toxic. TOC analysis showed that AZA has lowest (only 18%) and MAL has highest mineralization (56%). Considering the obtained results, it could be concluded that ClO2 efficiently degrades AZA, DM, FEN and MAL and represents good solution for a safer environment

Degradation herbicides with chlorine dioxide: degradation efficiency and toxicity test

The main objective of this study was to find optimal parameters for degradation of herbicides, such as nicosulfuron and thifensulfuron-methyl, with chlorine dioxide in deionized water. In order to examine the optimal parameters, degradation of herbicides was investigated under light or dark conditions with different amount of chlorine dioxide (5 and 10 ppm), different time of degradation (30 min, 1, 2, 3, 6 and 24 h) and at different pH values (3, 7 and 9). Degradation efficiency of herbicides was monitored using HPLC-DAD. Acute toxicity tests were performed for degradation products after the treatment with chlorine dioxide