A Review Of New Trends In Lactide Polymerisation Based On Metal Complexes

No Abstrac

Poly(ester-ether)s: I. investigation of the properties of blend films of polydioxanone and poly(methyl dioxanone)

This study aimed at examining the properties of blends of semi-crystalline polydioxanone (PDX) and amorphous poly(methyl dioxanone) (PMeDX). The authors show that low amounts of PMeDX, within 15 wt% acts as plasticizer to high molar mass PDX as confirmed by an increase in Young\u27s modulus of films. The plasticizing effect on blends increased with decreasing reduced viscosity of PMeDX. Mechanical tests showed overall reduced tensile properties of the blends. Viscosity analysis coupled with SEM and AFM indicated immiscibility of the blends over the whole range of compositions. Blend samples with higher PMeDX contents degraded at faster rates with profiles differing from PDX. © 2014 Copyright Taylor & Francis Group, LLC

Poly(ester-ether)s: III. assessment of cell behaviour on nanofibrous scaffolds of PCL, PLLA and PDX blended with amorphous PMeDX

The aim of this paper is to investigate the physico-chemical properties, degradation behaviour and cellular response of electrospun fibre-scaffolds of semi-crystalline PCL, PLLA and PDX blended with amorphous poly(methyl dioxanone) (PMeDX). Electrospun PCL/PMeDX and PLLA/PMeDX blend mats in varying weight ratios of the two components were fabricated and their overall performance was compared with similar composition PDX/PMeDX scaffolds. DSC analysis showed almost no change in crystallization temperature of PCL with increasing PMeDX content and TGA showed a different degradation profile as PMeDX content increased. The appearance of two crystallization peaks for PLLA/PMeDX blends suggested stereocomplex formation. As noted from AFM images, addition of PMeDX caused a change in the width of the lamellae from 14.8 ± 2.9 nm in 100/0 mat to 32.0 ± 11.5 nm in 85/15 mat. Moreover, PCL/PMeDX blend mats show a significant drop in Young\u27s modulus for 93/7, 90/10 and 85/15 compositions compared to 100/0 and 98/2. On the other hand, no clear trend in mechanical properties was observed for espun PLLA/PMeDX mats with increasing PMeDX content. Based on these analyses, it was concluded that PCL and PMeDX were immiscible while miscible blends were obtained with PLLA and PMeDX. Initial degradation of electrospun mats over a period of 5 weeks appears to occur via a surface erosion mechanism. In vitro cell culture studies using HDFs showed that the scaffolds were bioactive and a greater density of viable cells was noted on electrospun PCL/PMeDX and PLLA/PMeDX scaffolds compared to PCL and PLLA mats respectively. HDFs infiltrated through the entire thickness of espun 85/15 PLLA/PMeDX scaffold due to a combination of factors including morphology, porosity, surface characteristics and mechanical properties. This journal i

Poly(ester-ether)s: II. Properties of electrospun nanofibres from polydioxanone and poly(methyl dioxanone) blends and human fibroblast cellular proliferation

This article deals with an in-depth study of the thermal, mechanical and degradation behaviours of nanofibres from polydioxanone (PDX) and polydl-3-methyl-1,4-dioxan-2-one (PMeDX) and a comparison with their blend films. Varying ratios of both polymers were blended and electrospun from solution. Electrospun fibres exhibited a melting transition at 109°C independently of the PMeDX content, which corresponds to the melting of PDX nanofibres. As a result of the drawing process, PMeDX had a reduced plasticizing effect on PDX. In general, it was observed that overall crystallinity of the fibres decreased from 53% to 36% with increasing PMeDX content and this impacted on their mechanical properties. The Young\u27s moduli decreased as the PMeDX content of the fibres increased. However, an increase in strain at break and peak stress was noted as a result of a decrease in the fibre diameter. AFM images of the electrospun fibres showed an increasing degree of morphological heterogeneity with increasing PMeDX content. Thermal degradation studies showed that electrospun mats were thermally more stable than blend films, as confirmed by a two-fold increase in activation energy. The hydrolytic degradation of the electrospun mats conducted in phosphate buffer solution at 37°C showed that the degradation followed a surface erosion mechanism as opposed to bulk degradation observed for blend films. Degradation of fibres was found to be mainly dependent on their diameter. On the other hand, the degradation of blend films depended on the overall crystallinity of the blends. Electrospun PDX/PMeDX nanofibrous scaffolds were also subjected to cell viability studies with human dermal fibroblasts, in which they did not show illicit response and demonstrated excellent cell attachment and proliferation. © 2014 The Royal Society of Chemistry

Poly(ester-ether)s: I. Investigation of the Properties of Blend Films of Polydioxanone and Poly(methyl dioxanone)

<div><p>This study aimed at examining the properties of blends of semi-crystalline polydioxanone (PDX) and amorphous poly(methyl dioxanone) (PMeDX). The authors show that low amounts of PMeDX, within 15 wt% acts as plasticizer to high molar mass PDX as confirmed by an increase in Young's modulus of films. The plasticizing effect on blends increased with decreasing reduced viscosity of PMeDX. Mechanical tests showed overall reduced tensile properties of the blends. Viscosity analysis coupled with SEM and AFM indicated immiscibility of the blends over the whole range of compositions. Blend samples with higher PMeDX contents degraded at faster rates with profiles differing from PDX.</p> </div