Organothiol (R-SH) (OT) adsorption onto silver nanoparticles (AgNPs) in water was studied for a series of aromatic OTs including p-methylbenzenethiol (p-MBT), p-benzenedithiol (p-BDT), and 2-mercaptobenzimidazole (2-MBI). Unlike the common view that OT forms monolayer adsorption on AgNPs, we found that these aromatic OTs continuously reacted with AgNPs through formation of RS–Ag complexes until complete OT or AgNP consumption occurred. The RS–Ag complex can remain on the AgNP surface, converting the AgNPs into core–shell structures. The OT adsorption onto AgNPs occurs predominately through reaction with silver oxide present on the AgNP surfaces before the OT addition or formed from environmental oxygen in the presence of OT. The RS–H protons are completely released when both p-MBT and 2-MBI reacted with AgNP, Ag2O, and AgNO3. However, a substantial fraction of S–H bonds remained intact when p-BDT, the only dithiol used in this work, is adsorbed on AgNPs or reacted independently with Ag2O and AgNO3. The new insights from this work should be important for understanding OT interaction with AgNPs in water and the SERS spectra of the OT adsorbed onto AgNPs.

Self‐assembly and mechanical properties of triblock copolymers in a mid‐block selective solvent are of interest in many applications. Herein, we report physical assembly of an ABA triblock copolymer, [PMMA–PnBA–PMMA] in two different mid‐block selective solvents, n‐butanol and 2‐ethyl‐1‐hexanol. Gel formation resulting from end‐block associations and the corresponding changes in mechanical properties have been investigated over a temperature range of −80 °C to 60 °C, from near the solvent melting points to above the gelation temperature. Shear‐rheometry, thermal analysis, and small‐angle neutron scattering data reveal formation and transition of structure in these systems from a liquid state to a gel state to a percolated cluster network with decrease in temperature. The aggregated PMMA end‐blocks display a glass transition temperature. Our results provide new understanding into the structural changes of a self‐assembled triblock copolymer gel over a large length scale and wide temperature range. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 877–887

A series of poly(amino (meth)acrylate) brushes, poly(2‐(dimethylamino)ethyl methacrylate) (PDMAEMA), poly(2‐(diethylamino)ethyl methacrylate) (PDEAEMA), poly(2‐(dimethylamino)ethyl acrylate) (PDMAEA), poly(2‐(tert‐butylamino)ethyl methacrylate) (PTBAEMA), has been synthesized via surface‐confined controlled/living radical polymerizations using surface‐confined initiator from silane self‐assembled monolayers (SAMs) on silicon (Si) wafer substrates. Chemical methods and efficacies for two types of living radical polymerization, atom transfer radical (ATRP) and single electron transfer (SET‐LRP), are described and contrasted for the surface confined polymerization of poly(amino (meth)acrylate)s. Effects of solvent, catalyst/ligand system, and temperature on polymerization success were examined. Chemical compositions after each reaction step were characterized with FTIR spectroscopy, contact angle goniometry, and X‐ray photoelectron spectroscopy while the SAM and polymer brush thicknesses were measured with spectroscopic ellipsometry. For the first time, this study demonstrates successful surface‐confined polymerization of a series of poly(amine (meth)acrylate) brushes from Si‐SAM substrates using a copper metal electron donor catalyst. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6552–6560, 2009

Chitosan, a biopolymer found in the exoskeletons of shellfish, has been shown to be antibacterial, biodegradable, osteoconductive, and has the ability to promote organized bone formation. These properties make chitosan an ideal material for use as a bioactive coating on medical implant materials. In this study, coatings made from 86.4% de-acetylated chitosan were bound to implant-quality titanium. The chitosan films were bound through a three-step process that involved the deposition of 3-aminopropyltriethoxysilane (APTES) in toluene, followed by a reaction between the amine end of APTES with gluteraldehyde, and finally, a reaction between the aldehyde end of gluteraldehyde and chitosan. Two different metal treatments were examined to determine if major differences in the ability to bind chitosan could be seen. X-ray photoelectron spectroscopy (XPS) was used to examine the surface of the titanium metal and to study the individual reaction steps. The changes to the titanium surface were consistent with the anticipated reaction steps, with significant changes in the amounts of nitrogen, silicon, and titanium that were present. It was demonstrated that more APTES was bound to the piranha-treated titanium surface as compared to the passivated titanium surface, based on the amounts of titanium, carbon, nitrogen, and silicon that were present. The metal treatments did not affect the chemistry of the chitosan films. Using toluene to bond APTES on titanium surfaces, rather than aqueous solutions, prevented the formation of unwanted polysiloxanes and increased the amount of silane on the surface for forming bonds to the chitosan films. Qualitatively, the films were more strongly attached to the titanium surfaces after using toluene, which could withstand the ultrahigh vacuum environment of XPS, as compared to the aqueous solutions, which were removed from the titanium surface when exposed to the ultrahigh vacuum environment of XPS.

Many polymer films are produced by extruding the polymer in a cast-or blown-film process. Often an additive is preblended into the polymer and, once the film is formed, the additive migrates to the film surface(s). Erucamide is a migratory additive that is commonly placed in polyolefin films to reduce their coefficient of friction (COF). The aim of this study was to examine the relationship between erucamide surface concentration and COF of LLDPE films. The erucamide surface concentration was varied in two ways. In one set of experiments, a film containing 5,000 ppm of erucamide was surface-washed with solvent and/or aged at room temperature for specific time periods. In another set, films with different erucamide bulk loadings were aged for 7 days to achieve different equilibrium surface concentrations. The surface concentration was measured by using surface washing, and the bulk loading was quantified by using microwave extraction. A plot of COF as a function of surface concentration showed that all of the results fell on a single curve, regardless of the method used to regulate the erucamide surface concentration. At a surface concentration of ϳ0.5 g/cm 2 , the kinetic COF began to plateau to a value less than or equal to ϳ0.2 for this erucamide-LLDPE system. J. VINYL ADDIT. TECHNOL., 11:9 -12, 2005.