Mechanical Investigations Of The Primary Cell Wall And Attempts At Modification Of Novel Core Adhesives For Use In Iron Foundries

Open Access
Author:
Munson, Paul Jonathan
Graduate Program:
Chemistry
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
August 11, 2014
Committee Members:
  • Danny Glynn Sykes, Thesis Advisor
  • Nicole Robitaille Brown, Thesis Advisor
Keywords:
  • Primary Cell Wall
  • DMA
  • Pectin
  • Binders
  • MEMS
Abstract:
1. The primary cell wall of plants display interesting mechanical properties such as stiffness to resist the turgor forces generated by the living cell and extensibility to allow it to grow. The interactions occurring between the polysaccharides cellulose, xyloglucan (XG), and pectin were examined thermo-mechanically. Heat treatment of plant tissues for brief periods (<15 min) resulted in an increase in the stiffness of the tissues in the linear viscoelastic region of up to 46% compared to controls. Heat treatment of tissues containing little or no xyloglucan (celery parenchyma and xxt1/xxt2 Arabidopsis mutants) result in higher stiffness after heating of up to 60% which leads to the thought that XG rearrangement may not be the major cause of the stiffness. Rearrangement of the pectin / cellulose matrix is the major factor. This agrees with sum frequency generation (SFG) data that show a re-dispersement of cellulose during heating in tests involving onion epidermal cell walls. X-ray spectroscopy also revealed no aggregation of cellulose microfibrils occurring during heating. Microelectromechanical System (MEMS) testing was accomplished on heat treated onion epidermal cell wall to distinguish if the stiffness was primarily caused at the tissue level or at the single wall level. Results indicated that the wall section became less stiff after heat treatment, which implicates the tissues and possible the middle lamella in the stiffening. The cell wall sections however show greater strength at break of 46% than controls and have a higher strain of 67%. This indicates that the cell wall structure is undergoing rearrangement during heating, and that no one factor is decisive in the observed stiffening.