Effect Of End-group Functionality Research Articles

Polyester Macromonomer Syntheses and Radical Copolymerization Kinetics with Styrene

Short-chain polyester methacrylate macromonomers with alkyl, tertiary amine, carboxyl, and hydroxyl end-group functionalities are synthesized by ring-opening polymerization and subsequent modification. Monomer conversion and composition drift during batch radical copolymerizations of (macro)monomer with styrene are tracked using the in situ NMR technique in both polar and nonpolar deuterated solvents at 80 °C. For experiments with initial methacrylate molar fraction fxMA = 0.2, the effects of end-group functionality, solvent, and hydrogen bonding on relative reactivity are pronounced for monomeric analogues of the macromonomers. However, the polyester spacers significantly dilute these effects in macromonomer copolymerization, as polyester type, length, and end-group functionality did not influence copolymerization kinetics. Instead, the chemical identity up to several units from the methacryloyl group is the most important indicator of macromonomer relative reactivity.

Substrate selective patterning on lithography defined gold on silica: Effect of end-group functionality on intermolecular layer formation

An increasing number of applications in nanobiotechnology and other areas call for defined regions of different chemical functionality to achieve site-specific attachment while minimizing any unwanted surface interactions. In order to generate spatially defined chemical patterns on planar surfaces, standard nanofabrication methods are typically employed. However, when incorporating biological and chemical molecules into complex nanofabricated structures the micro/nanofabrication methods needed are often incompatible with the standard approaches used to achieve chemical patterning. An alternative strategy is to use substrate selective patterning (SSP) where two different organic molecules each have a specific affinity to a particular substrate material via a surface anchoring group. Here we use imaging ellipsometry, an ideally suited technique for measuring monolayer films on patterned substrates, and infrared spectroscopy to investigate SSP of alkanethiols with hydrophilic/hydrophobic moieties in combination with a methoxypolyethylenoxypropyltrichlorosilane reagent (mPEGTCS) on patterned gold on native silicon oxide substrates. One central aspect of SSP that was investigated was the cross-reactivity between the various substrate specific molecules, which can cause multilayer formation. Results showed that when the mPEGTCS reagent was used subsequently after formation of hydrophilic self-assembled alkanethiol monolayers (SAMs), there was an additional layer build-up of silane. No multilayer formation was observed for a hydrophobic alkanethiol SAM. SSP can be a practical method to effectively create localized functional chemistry on spatially defined nanofabricated devices.

Surface energy and adhesion of perfluoropolyether nanofilms on carbon overcoat: The end group and backbone chain effect

In this paper, we have investigated the surface energy and adhesion of one functional PFPE (Zdol) and two series of nonfunctional PFPEs (Z and D) on carbon-overcoated disk surfaces. The effects of end group functionality, backbone chain flexibility, molecular weight, and film thickness were systematically examined. Our results indicated that nonfunctional PFPEs have weak attraction with carbon overcoat. However, due to backbone chain effect, Z has slightly stronger attraction than D. Based on the surface energy analyses and bonded thickness results, schematic bonding models were proposed, which indicate strong hydrogen bonding∕ordered packing structure∕low mobility for functional PFPE films and weak attraction∕less-ordered packing structure∕high mobility for nonfunctional PFPE films.

Pyrene Fluorescence as a Molecular Probe of Miscibility in Organic/Inorganic Hybrid Nanocomposites Suitable for Microelectronic Applications

AbstractFluorescence spectroscopy has been used to study the miscibility of methyl silsesquioxane (MSSQ)/poly(methyl methacrylate-co-dimethylaminoethyl methacrylate) [P(MMA-co-DMAEMA)] hybrid nanocomposites, which are useful in fabricating the next generation of spin-on, ultra-low dielectric constant materials in the microelectronic industries. In this work, we have attached the pyrene group into the PMMA side chains. MSSQ with different amount of initial -SiOH (silanol) endgroups are used to study the effect of endgroup functionality on the phase separation behavior of the hybrid nanocomposites. Pyrene excimer fluorescence results reveal that MSSQ is miscible with P(MMA-co-DMAEMA) only up to 6 wt% P(MMA-co-DMAEMA) loading level, thus establishing an upper limit on local miscibility with MSSQ. As the P(MMA-co-DMAEMA) loading level increases, the excimer to monomer ratios also increase, suggesting that the MSSQ/P(MMA-co-DMAEMA) hybrid nanocomposites move toward greater immiscibility. This ratio approaches that of the neat polymer for domain sizes > 5 nm (SAXS, SANS). The fluorescence results also show that, the lower the amount of initial silanol groups in MSSQ, the greater the immiscibility of the MSSQ and porogen, which ultimately translates into larger pores upon porogen burnout.

Monte Carlo simulations of liquid spreading on a solid surface: effect of end-group functionality.

The spreading of liquid droplets composed of molecules with or without reactive end groups over a solid surface has been studied using Monte Carlo simulations. For molecules without reactive end groups, a molecular layering in the spreading profiles is predicted, depending on the ratio of the magnitude of intermolecular interactions to thermal energy. As intermolecular interactions become smaller than thermal energy, the layered structure vanishes. For molecules with reactive end groups, interactions between end groups and between end groups and the surface complicate the situation. By assuming an end-to-end interaction between molecules and the pinning of end groups to the surface, a complex layered structure is obtained. Our simulation predicts spreading profiles that accurately describe the broad spectrum of data obtained from scanning microellipsometry for perfluoropolyalkylethers with and without reactive end groups.

Properties of radiation cured coatings

Coatings were prepared from acrylate or methacrylate functionalized resins to study the effect of end group fnctionality on the physical properties of u.v. and electron beam cured coatings. Cure response was measured by solid state NMR and gel extraction, as expected, methacrylate resins cured much slower. Thermal Gravimetric Analysis (TGA) revealed acrylate coatings have greater thermal stability. Properties such as tensile strength and hardness showed little effect of end group functionality or curing method. The O 2 and H 2O permeabilities of the coating were correlated with rhe processing conditions.