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Controlling Polymer Properties Through Attenuating Intermolecular Interactions
Attenuating intermolecular interactions can result in enhancing properties or even can lead to new properties. Attenuating intermolecular and interchain interactions in polymeric materials can be achieved through the structural design and complex blend preparation. In this study, both approaches have been employed for organic materials with the focus on ion exchange membranes and inorganic materials developed by sol-gel chemistry. Manipulating intermolecular interactions through designing a branched poly(arylene ether sulfone) (BPAES) copolymer with various side-chain lengths led to change in molecular aggregation in solution and affected polymer thermal and mechanical properties in the film. Results showed the existence of optimum side-chain length for achieving highest mechanical robustness. However, a further increase in side-chain length would negatively affect intermolecular interactions and would lead to steric crowding and lowering the toughness of materials. Furthermore, this newly designed structure with sulfonated side-chain (sBPAES) was introduced to the matrix of fully aromatic sulfonated polyphenylene sPP to enhance its properties for proton exchange membrane fuel cell application. The ionic interaction induced by the sulfonated side-chain dramatically improved miscibility between these distinctly different ionomers and affected the polymer morphology and water distribution in the polymer. These modifications led to an increase in fractional free volume and relative free water content in the polymer and consequently resulted in increased conductivity by 4% and decreased water uptake by 25% for sPP:sBPAES(95:5) blend in comparison with pristine sPP. Optimized intermolecular interactions in blend containing 5 wt% sBPAES within sPP led to hydrogen-oxygen peak-power output of 630 mW/cm2 at 1490 mA/cm2, which was greater than its unmodified sPP version at 570 mW/cm2 and 1220 mA/cm2. Effect of intermolecular interactions on polymer properties was further studied for inorganic materials developed via sol-gel chemistry to produce homogenous electrospun nanofibers. Altering the inorganic network by changing the density of Si-O-Ti, Ti-O-Ti ,and Si-O-Si while the extent of network formation was similar resulted in bead formation for samples containing more than 50 mol% of titania. In addition, statistical analysis study on SiO2-TiO2 nanofibers with similar 1:1 molar ratio showed optimizing interactions between electrospinning conditions and extent of network formation can transform broken nanofibers to homogenous continuous nanofibers.
Polymer chemistry|Chemical engineering
Motealleh, Behrooz, "Controlling Polymer Properties Through Attenuating Intermolecular Interactions" (2019). ETD collection for University of Nebraska - Lincoln. AAI13863882.