Thesis Title: STRUCTURE-PROPERTY RELATIONSHIPS OF GEL-SPUN POLY(VINYL ALCOHOL) AND CARBON NANOTUBE COMPOSITE FIBERS

ABSTRACT

The process of gel spinning has been employed- because of its utility in producing high strength, high modulus fibers of poly(vinyl alcohol), PVA.  Researchers have embedded single walled carbon nanotubes (SWNTs) into the matrix of gel-spun PVA fibers for the two-fold purpose of templating molecular chain extension and for bearing mechanical stress.  The dispersion and exfoliation of embedded SWNTs can influence the efficacy of load transfer.  Molecular interactions between carbon nanotubes (CNTs), the matrix polymer, and the dispersing solvent are known to influence interfacial adhesion and the distribution of CNTs throughout the polymer composite.

The structure-property relationships of stage-drawn PVA and SWNT composite fibers are described herein.  The mechanical properties, thermal behaviors, and microstructures of gel-spun fibers were characterized at several stages of heat drawing.  Evidence of the molecular chain extension of PVA has been supported by thermal analysis and IR spectroscopy.  Structural deviations from the idealized microstructure include lamellar crystals, solvated polymer, and the misalignment of polymer microphases and SWNTs.

Uniaxially aligned SWNTs were found to influence the aligning of electron donating and withdrawing moieties of PVA and DMSO.  The aligning of PVA’s functional groups has been attributed to non-covalent bonding, i.e. electronic field effects between SWNTs and PVA’s hydroxyl and carbonyl moieties.  The sulfoxide moieties of DMSO imbibed in SWNT composite fibers preferentially aligned normal to the fibers axis, however no preferential orientation was observed among unfilled PVA fibers.  Nearly 40 % of imbibed DMSO is influenced by the orientation of embedded SWNTs.

Literature has reported ageing to have a positive affect on the drawability of PVA gels.  The ageing of PVA/CNT gels in being carried out in the current study.  The structure and properties of PVA/CNT fibers processed with varying gelation histories are under investigation.