Advancing characterization techniques for structure-property determination of in-situ lignocelluloses

The global progression towards sustainable energy, materials and chemicals requires novel and improved analytical tools to understand and optimize lignocellulosic biomass utilization. In an effort to advance lignocellulose characterization, gain insights into biomass processing, and obtain novel perspectives on cell wall ultrastructure, this study utilizes three principal polymer characterization techniques, namely compressive-torsion dynamic mechanical analysis (DMA), deuterium quadrupolar nuclear magnetic resonance (2H NMR) and rheo-infrared spectroscopy. A novel parallel-plate compressive-torsion DMA protocol is developed to analyze very small solvent-plasticized biomass specimens with or without mechanical integrity. The benefits and limitations of this technique are demonstrated by comparing it to a conventional tensile-torsion DMA while analyzing various solvent-plasticized lignocelluloses. The rheology of wood in various organic solvents is studied through dynamic thermal scans, Time/temperature superposition (TTS) and fragility analysis. Plasticizing solvents and wood grain orientation significantly affected the lignin glass-transition temperature. Dynamic TTS reveals that while all storage modulus data shift smoothly, the thermorheological complexity of solvent-plasticized wood becomes evident in loss component master curves. It is argued that the plasticized lignocellulose TTS is insightful and potentially useful, although it fails to satisfy the classic TTS validity criteria. Subsequently, it is justified that the fragility analysis is a better suited treatment than the WLF model to investigate cooperative segmental motions of plasticized wood. Deuterium quadrupolar NMR reveals a new perspective on the orientation of amorphous wood polymers and two distinct amorphous polymer domains: a highly oriented phase in the S2 layer of the secondary cell wall and an isotropic phase postulated to occur in the compound middle lamella (CML). If the origin of the isotropic phase is confirmed to arise from the CML, then this technique provides a way to independently investigate the morphology and phase dynamics of CML and S2 in an intact tissue, and should bring novel insights into deconstructive strategies specific to the oriented and unoriented domains. Finally the effects of a wood-adhesion promoter (hydroxymethyl resorcinol, HMR) on in-situ wood polymers are studied to elucidate the still unresolved HMR-lignocellulose interactions. DMA, creep-TTS and 2H NMR reveal that HMR increases the crosslink density and restricts the mobility of wood amorphous phase. Rheo-IR spectroscopy shows that the molecular stress-transfer mechanism is altered within the wood cell wall.

Name thesis:degree_name

Ph. D.

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Macromolecular Science and Engineering

Department dc:contributor.department

Macromolecular Science and Engineering

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

2011

Author dc:creator

• Chowdhury, Sudip

Chair dc:contributor.committeechair

• Frazier, Charles E.

Committee members dc:contributor.committeemember

• Wilkes, Garth L.
• Barone, Justin R.
• Renneckar, Scott H.
• Moore, Robert Bowen
• Madsen, Louis A.

• biomass fractionation
• wood-adhesion promoter
• infrared spectroscopy
• NMR
• quadrupolar interaction
• DMA

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Dc Identifier Other

etd-08222011-194452

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/39189