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Document Type

Open Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Degree Program

Polymer Science and Engineering

Year Degree Awarded

2015

Month Degree Awarded

February

First Advisor

Tew, Gregory N.

Second Advisor

Hayward, Ryan C.

Third Advisor

Tuominen, Mark

Subject Categories

Polymer Science

Abstract

Bicontinuous structures are beneficial to many applications from health and medicine to energy and the environment. Although these materials can be used for many applications, current strategies yield bicontinuous structures only under highly specific processing conditions. Development of a versatile platform to reliably obtain bicontinuous morphologies will be broadly beneficial. This work presents two platforms that can be used to produce bicontinuous morphologies using a simple Mitsunobu/thiol-ene strategy. This platform allows for the incorporation of a variety of polymer chemistries to yield well-defined polymer networks or multiblock copolymers (MBCs). It also allows for the systematic investigation of factors affecting the morphology such as the molecular weight between cross-links and the volume fraction of the network components. The ease at which these variables can be systematically investigated allows for rigorous fundamental studies of these composite systems.

In the first co-network system, the platform’s ability to tailor mechanical properties while maintaining good ion conductivity was demonstrated by comparing PEG-PDMS co-networks to PEG networks using EIS and DMA. Also, the effect of salt loading on thermal properties was explored using DSC. The second system, PEG-PS co-networks, demonstrated that varying the molecular weight of the precursor polymers results in control over d-spacing that fits well to de Gennes’s prediction (d ~ Mn0.5). Despite the variation in d-spacing, 22 - 55 nm, the ion conductivity and mechanical properties remained relatively consistent, demonstrating versatility in this system. Critical percolation thresholds were investigated by using ion conductivity and storage modulus to probe the continuity of the PEG and PS phases, respectively. Percolation theory suggests this system has a wide bicontinuous compositional window from fPEG = 0.225 -0.675. A preliminary phase diagram was generated by combining results from the molecular weight and volume fraction series. Finally, a simple synthesis for (MBCs) is demonstrated using the same Mitsunobu/thiol-ene platform. MBCs with ~4 blocks and two or three types of macromonomers were synthesized. Disordered phase separation was shown by SAXS and AFM. The versatile Mitsunobu/thiol-ene platform is easily able to synthesize different architectures using a range of polymer chemistries for various morphology and property studies.

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