Emily M. Parker

Post-polymerisation modification of surface chemical functionality and its effect on protein binding

Derivatisation of polystyrene by carbene insertions followed by diazonium coupling permits the introduction of diverse chemical functionality, providing access to materials with similar bulk properties, but in which surface chemical characteristics are systematically varied across a range of surface polarity, hydration and non-bonding interaction behaviour. Protein binding experiments with bovine serum albumin demonstrate that protein adhesion is dependent upon the identity of the surface chemical group, with tert-butyl, hexyl, dimethylamino, amino, and carboxyl modified systems all exhibiting higher levels of binding, while glycol, hydroxyl, and phosphonate give similar or lower levels of binding, relative to the control. This behaviour has been shown to be time dependent, and an approximate trend of protein binding with cheminformatic descriptors %PSA and contact angle was observed.

Surface Characterization and in situ Protein Adsorption Studies on Carbene-Modified Polymers.

Polystyrene thin films were functionalized using a facile two-step chemical protocol involving carbene insertion followed by azo-coupling, permitting the introduction of a range of chemical functional groups, including aniline, hexyl, amine, carboxyl, phenyl, phosphonate diester, and ethylene glycol. X-ray photoelectron spectroscopy (XPS) confirmed the success of the two-step chemical modification with a grafting density of at least 1/10th of the typical loading density (10(14)-10(15)) of a self-assembled monolayer (SAM). In situ, real-time quartz crystal microbalance with dissipation (QCM-D) studies show that the dynamics of binding of bovine serum albumin (BSA) are different at each modified surface. Mass, viscoelastic, and kinetic data were analyzed, and compared to cheminformatic descriptors (i.e., c log P, polar surface area) typically used for drug discovery. Results show that functionalities may either resist or adsorb BSA, and uniquely influence its adsorption dynamics. It is concluded that carbene-based surface modification can usefully influence BSA binding dynamics in a manner consistent with, and more robust than, traditional systems based on SAM chemistry.

New Routes to Functionalize Carbon Black for Polypropylene Nanocomposites

Methods for chemical surface functionalization for carbon black (CB) nanoparticles were studied to produce (CB)/polypropylene (PP) nanocomposites with superior electrical and thermal properties. Nanoparticle dispersion is known to directly control the extent to which nanocomposites maximize the unique attributes of their nanoscale fillers. As a result, tailored nanoparticle surface chemistry is a widely utilized method to enhance the interfacial interactions between nanoparticles and polymer matrices, assisting improved filler dispersion. In this work, a rapid chemical functionalization approach using a number of diarylcarbene derivatives, followed by the azo-coupling of substituted diazonium salts, for the covalent introduction of selected functional groups to the CB surface, is reported. Characterization of the modified CB by XPS, TGA, CHN, and ATR-IR collectively confirmed surface functionalization, estimating surface grafting densities of the order of 10(13) and 10(14) molecules/cm(2). Nanocomposites, synthesized by solvent mixing PP with pristine and modified CB, demonstrated macroscopic property changes as a result of the nanoparticle surface functionalization. Pronounced improvements were observed for PP nanocomposites prepared with a dodecyl-terminated diaryl functionalized CB, in which TEM analysis established improved nanofiller dispersion owing to the enhanced CB-PP interfacial interactions in the nanocomposite. Observed dielectric relaxation responses at 20 wt % loading and a reduced percolation threshold realized conductivities of 1.19 × 10(-4) S cm(-1) at 10 wt %, compared to 2.62 × 10(-15) S cm(-1) for pristine CB/PP nanocomposites at the same filler loading. In addition, thermal properties signify an increase in the number of nucleation sites by the raised degree of crystallinity as well as increased melting and crystallization temperatures.

ENGINEERING OF SURFACE FUNCTIONALITY ONTO POLYSTYRENE MICROCARRIERS FOR THE ATTACHMENT AND GROWTH OF HUMAN ENDOTHELIAL CELLS

This work reports the effects of introducing diverse chemical functionalities onto the surface of polystyrene microcarrier beads on their ability to function as injectable cell carriers. Cellular adhesion and proliferation, as well as cellular outgrowths from microcarrier surfaces, using human umbilical vein endothelial cells (HUVECs), were examined in detail. It was observed that initial cell adhesion appeared to be most significantly decreased by hydrophobicity, whilst cell proliferation appeared to be improved in most chemical functional groups over unmodified polystyrene. Overall, our study highlights the importance of surface chemistry in directing the growth and function of human endothelial cells.

Chemical functionalization of polyethylene surfaces by plasma-assisted carbene insertion

ABSTRACT Controlled surface modification of PE is achieved by an efficient and facile approach via plasma-assisted carbene insertion generated using diazo chemistry. The combination of plasma and carbene insertion shows a synergistic effect, which leads to an obvious enhancement of surface grafting, as shown qualitatively by a combination of IR and UV reflectance spectroscopy, and XPS analysis. The chemical modification may be observed spectroscopically, and the approach provides an opportunity for the convenient modification of low surface energy materials.