Materials Science and Engineering Commons^™

Chemical Modification Of Lignin Into Advanced Materials, Soheil Hajirahimkhan

Electronic Thesis and Dissertation Repository

Fossil fuel resources are being used today for most of humankind’s energy and chemical/material needs. The inevitable demise of these resources has created significant interest in the field of biomass and particularly, lignin valorization. As the world’s second most abundant polymer, more than 98% of the annually produced lignin is under-utilized either as an on-site heat source, or as landfill. Thus, finding practical approaches to modifying this inexpensive sustainable resource into materials of high value can be the next leap in lessening the dependence on fossil fuel resources and thus, developing a sustainable future.

In this thesis, kraft lignin is …

Microinjection Molding Of Carbon Filled Polymer Composites, Shengtai Zhou

Electronic Thesis and Dissertation Repository

There has been increasing demand for microparts in the areas of electronics, automotive, biomedical and micro-electro-mechanical systems. Microinjection molding (μIM) is becoming an important technology to fabricate miniature products or components to satisfy the ever-increasing needs of the above industries. Polymers and polymeric composites are ubiquitously adopted as molding materials due to their weight advantage, good processability and excellent resistance to corrosion.

Earlier studies have been primarily focused on the μIM of unfilled thermoplastics; however, microparts with multi-functionalities, such as electrical, thermal and mechanical properties are always accommodated by using multi-functional filler loaded polymer composites. Recently, μIM of carbon nanotubes …

Effect Of Material Viscoelasticity On Frequency Tuning Of Dielectric Elastomer Membrane Resonators, Liyang Tian

Electronic Thesis and Dissertation Repository

Dielectric elastomers (DEs) capable of large voltage-induced deformation show promise for applications such as resonators and oscillators. However, the dynamic performance of such vibrational devices is not only strongly affected by the nonlinear electromechanical coupling and material hyperelasticity, but also significantly by the material viscoelasticity. The material viscoelasticity of DEs originates from the highly mobile polymer chains that constitute the polymer networks of the DE. Moreover, due to the multiple viscous polymer subnetworks, DEs possess multiple relaxation processes. Therefore, in order to predict the dynamic performance of DE-based devices, a theoretical model that accounts for the multiple relaxation processes is …

Development And Applications Of Polyglyoxylate Self-Immolative Polymers, Bo Fan

Electronic Thesis and Dissertation Repository

Self-immolative polymers (SIPs) are relatively recent class of stimuli-responsive and degradable polymers that have attracted significant attention in the past several years. SIPs consist of polymer backbones and stimuli-responsive end-caps at one or both polymer termini. Upon detection of a stimulus, the decomposition of the end-cap leads to complete end-to-end depolymerization. Polyglyoxylates were introduced as a new class of polyacetal based SIPs by our group in 2014. Compared with other SIPs, polyglyoxylates have two advantages including: 1) readily available monomers and 2) low toxic depolymerization products. These advantages may allow polyglyoxylates to be used in a wide range of applications. …

Fabrication Of 3d Conjugated Polymer Structures Via Vat Polymerization Additive Manufacturing, Andrew T. Cullen

Electronic Thesis and Dissertation Repository

Conjugated polymers are a class of electromechanically active materials that can produce motion in response to an electric potential. This motion can be harnessed to perform mechanical work, and therefore these materials are particularly well suited for use as sensors and actuators in microelectromechanical systems. Conventional methods to fabricate conjugated polymer actuators result in planar morphologies that limit fabricated devices to simplistic linear or bending actuation modes. To overcome this limitation, this work develops a conjugated polymer formulation and associated additive manufacturing method capable of realizing three-dimensional conductive polymer structures. A light-based additive manufacturing technique known as vat polymerization is …

Covalently Crosslinked Organic/Inorganic Hybrid Biomaterials For Bone Tissue Engineering Applications, Dibakar Mondal

Electronic Thesis and Dissertation Repository

Scaffolds are key components for bone tissue engineering and regeneration. They guide new bone formation by mimicking bone extracellular matrix for cell recruitment and proliferation. Ideally, scaffolds for bone tissue engineering need to be osteoconductive, osteoinductive, porous, degradable and mechanically competent. As a single material can not provide all these requirements, composites of several biomaterials are viable solutions to combine various properties. However, conventional composites fail to fulfil these requirements due to their distinct phases at the microscopic level. Organic/inorganic (O/I) class II hybrid biomaterials, where the organic and inorganic phases are chemically crosslinked on a molecular scale, hence the …