The Synthesis of Hydroxybutyrate-Based Block Polyurethane from Telechelic Diols with Robust Thermal and Mechanical Properties

Dan Xue,Xiaodong Fan,Wei Lv,Zengping Zhang

doi:10.1155/2016/9635165

Dan Xue, Xiaodong Fan + Show 2 more

Open Access

https://doi.org/10.1155/2016/9635165

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Abstract

A series of novel amphiphilic block polyurethanes (PUHE) have been successfully synthesized by solution polymerization of the derived PHB-diol and poly(ethylene glycol) with a coupling agent of 1,6-hexamethylene diisocyanate (HDI), while the PHB-diol was prepared via the transesterification of PHB and ethylene glycol. The hydroxyl contents in PHB-diols range from 1.36 to 1.99 (the molar ratio) as determined by nonaqueous titration. The molecular weight and chemical compositions of PUHE and PHB-diol were investigated by GPC,1H NMR, and FTIR in detail, which confirm the successful synthesis of PUHE. The tensile strength and elongation at break of PUHE could reach as high as 20 MPa and 210%, as the content of PHB in PUHE is 33%. TGA curves indicate that block-bonding between PHB-diol and PEG increases the thermal stability of PHB-diol. Film degradation of PUHE was studied by weight loss and scanning electron microscope (SEM). It could be concluded that degradation occurred gradually from the surface to the inside and that the degradation rate could be controlled by adjusting the PHB/PEG ratios. These properties make PUHE able to be used as a biodegradable thermoplastic elastomer.

Highlights

Polyhydroxybutyrate (PHB) originated from bacteria has been considered one of the most prospective bioplastics [1, 2] due to excellent strength close to that of isotactic polypropylene and favorable melt processability [3, 4] for conventional process, such as extrusion [5, 6], moulding [7, 8], and spinning [9, 10]
Average molecular weights were determined by gel permeation chromatography (GPC) using chloroform as an eluent at a flow rate of 1.0 mL/min in Waters 1525 pump with a combination of four Styragel columns series (Styragel HR, 5 mm) and equipped with a 2414 differential refractive index detector and UV detector (Agilent Technologies PL-GPC 50 Integrated GPC System, USA)
The telechelic PHB with hydroxyl groups at both chain ends was successfully prepared by alcoholysis of PHB in the presence of p-toluenesulfonic acid as catalyst

Summary

Introduction

Polyhydroxybutyrate (PHB) originated from bacteria has been considered one of the most prospective bioplastics [1, 2] due to excellent strength close to that of isotactic polypropylene and favorable melt processability [3, 4] for conventional process, such as extrusion [5, 6], moulding [7, 8], and spinning [9, 10]. Polyurethane elastomer is a kind of block copolymer composed of soft and hard segments [27,28,29], which can be synthesized by the reaction between polymer terminated with free hydroxyl groups and difunctional isocyanates [30,31,32,33,34]. In the synthesis of polyurethane elastomer, mole ratio of NCO/OH shows a significant effect on the mechanical and hydrophilic performance. PHB oligomers terminated with free hydroxyl groups may be produced by the transesterification of alkane-diols with high molecular weight of PHB. It is still a challenge to quantify the terminal hydroxyl content in PHB oligomers and to study its effect on properties of the corresponding polyurethanes. The thermal and mechanical properties of as-prepared PUHE were studied to exploit its potential application as thermoplastic biodegradable elastomer

Experimental

Results and Discussion

Characterization of Proton Nuclear Magnetic Resonance

Conclusion