Research

[vc_row][vc_column][vc_project][vc_project_single project_image=”187″ project_title=”Viscoelastic Properties of Fluorocarbon Functionalized Polystyrene Films at the microscale by Nanoindentation”]Synthesis of a number of C7F15, C10F21 and C13F27 endfunctionalized low MW PS using atom transfer radical polymerization (ATRP) and its
effects on the viscoelastic properties of polystyrene (PS). As pointed out above, PFTD group is of special interest as association mediated by this group was shown to be stronger than the smaller RF groups. To the best of our knowledge these systems appear not to have been studied. Nanoindentation tests are employed to investigate the hypothesis that the mesogenic RF groups are more likely to prominently show the effects of formation of semicrystalline RF domains that mediate stronger inter-polymer association. In turn, this may result in improved mechanical properties. Polystyrene (PS) has been chosen as a model as it is a well-known and studied thermoplastic polymer with a number of desirable properties including high glass temperature, good processability and therefore use in applications in polymer electrolyte membrane fuel cells (PEMFCs), electronics and in block copolymers or their blends.[/vc_project_single][vc_project_single project_image=”190″ project_title=”Rheological Properties of PFTD Functionalized Polymers”]It is plausible that these RF end group effects would also be important in the bulk properties of PS and other homopolymers. For instance we have found that for C13F27 end-functionalized 15k PS the storage moduli were increased nearly two-fold while the loss moduli were increased about four fold. However, C13F27 end-functionalized 30k PS had similar storage modulus with PS 30k homopolymer at ambient temperature shown by nanoindentation measurements.[/vc_project_single][vc_project_single project_image=”192″ project_title=”Thermal and Optical Properties of Perfluoroalkyl End-Functionalized Polystyrenes Using Optical Transmission and Differential Scanning Calorimetry”]We report optical transmission data of films of these PFTD and other RF end functionalized PS with MW’s between 10 and 30k Dalton that show clear evidence of the formation of PFTD groups that aggregate into large (400 nm) domains of unknown shape but approximate sizes. In addition, DSC data indicate sizable decreases in Tg (as high as 15 0C) of the PFTD end functionalized PS compared to the isobaric PS. This surprising and seemingly unprecedented finding hints at a high PS mobility mediated by the chain end segments being connected to the PFTD aggregates.[/vc_project_single][vc_project_single project_image=”194″ project_title=”Optical, Thermal and Viscoelastic Properties of isobutyl Polyhedral Oligomeric Silsesquioxanes (POSS)-end functionalized PS”]It has been shown that self-assembly and association of RF groups lead to increased thermal and viscoelastic properties of PS. Similarly, POSS groups are known to form aggregates when they were blended into a polymer matrix or copolymerized.Previously, the degree of association of RF end groups was shown to be much more pronounced compared with RF pendent groups16-18 It is possible same principle also applies for POSS polymers. We synthesized POSS end functionalized PS with different MWs to investigate the effect of isobutyl POSS end functionalization on thermal, optical and rheological properties of PS.[/vc_project_single][vc_project_single project_image=”196″ project_title=”Development of Increased Flow Graphene Oxide-Polymer Nanocomposite Membranes”]Because of the various limitations of existing membranes there is still a need for finding alternative membranes that will have better water flux and salt rejection in addition to good resistance to fouling and degradation. Graphene has recently gained attention due to its unique properties. Graphene is a single layer of graphite with one atom thickness, consisting of a lattice of hexagonally arranged sp2-bonded atoms. It is an inexpensive and strong material. Especially graphene oxide (GO) has gained much attention since it offers excellent potential for making nanocomposite materials having improved stability, hydrophilicity and superior antibacterial and antifouling properties. GO membranes were shown to be impermeable to liquids, vapors and gases including helium whereas they had unimpeded permeation of water. However, pure GO membranes are easily leached out of their support under high hydrophilic environment and transmembrane pressure. In order to overcome this problem, we incorporated GO in PA matrix in order to investigate its potential to improve water flux without leaching problems.
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