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Related Experiment Videos

Autoxidation of medium chain length polyhydroxyalkanoate.

Manfred Schmid1, Axel Ritter, Andreas Grubelnik

  • 1Empa, Swiss Federal Laboratories for Materials Testing and Research, Laboratory for Biomaterials, Lerchenfeldstrasse 5, CH-9014 St. Gallen, Switzerland. manfred.schmid@empa.ch

Biomacromolecules
|February 13, 2007
PubMed
Summary

The autoxidation of medium chain length polyhydroxyalkanoates (mcl-PHA) biopolymers depends on double bond content. High unsaturation leads to cross-linking, while low unsaturation causes chain scission, impacting material stability.

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Area of Science:

  • Polymer Science
  • Materials Science
  • Biotechnology

Background:

  • Polyhydroxyalkanoates (PHAs) are versatile biopolymers with diverse applications.
  • Autoxidation (aging) is a known phenomenon in synthetic polymers, but less understood in biopolymers.
  • Medium chain length PHAs (mcl-PHA) are under investigation for their material properties.

Purpose of the Study:

  • To investigate the autoxidation behavior of mcl-PHA with varying levels of olefinic side chains.
  • To understand how double bond content affects the chemical and physical properties of mcl-PHA during aging.
  • To predict the shelf-life and stability of mcl-PHA based on oxidation kinetics.

Main Methods:

  • mcl-PHA copolymers with 0-75 mol% olefinic side chains were aged at 60°C in air for 3 months.

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  • Samples were analyzed weekly using sol-gel analysis, size exclusion chromatography (SEC), IR, and GC/FID.
  • Isothermal DSC experiments were performed to study oxidation kinetics.

    • Main Results:

    • The degree of unsaturation significantly influenced mcl-PHA autoxidation.
    • Low double bond content (0-10 mol%) resulted in polymer chain scission.
    • High double bond content (50-75 mol%) led to cross-linking and insolubility within weeks.

    Conclusions:

    • mcl-PHA's sensitivity to autoxidation is strongly dependent on its double bond content.
    • Storage at low temperatures (≤ -5°C) and under inert gas or with antioxidants is recommended for mcl-PHA.
    • Understanding these aging mechanisms is crucial for optimizing PHA applications and predicting material lifespan.