Effect of Molecular Weight of Methylphenylsiloxy-Containing Vinyl-Functionalized Terpolysiloxanes on Their UV-Activated Crosslinking by Hydrosilylation and Mechanical Properties of Crosslinked Elastomers.

Effects of molecular weight of methylphenyl-containing vinylsiloxy-functionalized terpolysiloxanes on their UV-activated crosslinking by hydrosilylation at room temperature in air, shelf life stability of "all-in-one" pastes prepared from them for additive manufacturing, and mechanical properties of the resulting crosslinked elastomers, are investigated. It is found that while rheology of pastes containing base polymers, trimethylsilylated silica fillers, and thixotropic additives is not significantly affected by the base polymer molecular weight but is dominated by the filler concentration, the pastes based on higher molecular weight polymers exhibit faster crosslinking (corresponding to higher catalyst turnover numbers) and their crosslinked elastomers show transient strain-induced crystallization. The latter appears in networks from terpolymers with degrees of polymerization (DP) of 240 and above (corresponding to about one half of the critical polydimethylsiloxane chain length for entanglement formation of DP = 460), within the temperature range of -80 to -30 °C, characteristic for polydimethylsiloxane melting transition.

Resolving transitions in the mesoscale domain configuration in VO2 using laser speckle pattern analysis.

The configuration and evolution of coexisting mesoscopic domains with contrasting material properties are critical in creating novel functionality through emergent physical properties. However, current approaches that map the domain structure involve either spatially resolved but protracted scanning probe experiments without real time information on the domain evolution, or time resolved spectroscopic experiments lacking domain-scale spatial resolution. We demonstrate an elegant experimental technique that bridges these local and global methods, giving access to mesoscale information on domain formation and evolution at time scales orders of magnitude faster than current spatially resolved approaches.

Methanol fractionation of softwood Kraft lignin: impact on the lignin properties.

The development of technologies to tune lignin properties for high-performance lignin-based materials is crucial for the utilization of lignin in various applications. Here, the effect of methanol (MeOH) fractionation on the molecular weight, molecular weight distribution, glass transition temperature (Tg ), thermal decomposition, and chemical structure of lignin were investigated. Repeated MeOH fractionation of softwood Kraft lignin successfully removed the low-molecular-weight fraction.

Lectin-functionalized poly(glycidyl methacrylate)-block-poly(vinyldimethyl azlactone) surface scaffolds for high avidity microbial capture.

Microbial exopolysaccharides (EPS) play a critical and dynamic role in shaping the interactions between microbial community members and their local environment. The capture of targeted microbes using surface immobilized lectins that recognize specific extracellular oligosaccharide moieties offers a nondestructive method for functional characterization of EPS content. In this report, we evaluate the use of the block copolymer, poly(glycidyl methacrylate)-block-4,4-dimethyl-2-vinylazlactone (PGMA-b-PVDMA), as a surface scaffold for lectin-specific microbial capture.

Poly(3-hexylthiophene) Molecular Bottlebrushes via Ring-Opening Metathesis Polymerization: Macromolecular Architecture Enhanced Aggregation.

We report a facile synthetic strategy based on a grafting through approach to prepare well-defined molecular bottlebrushes composed of regioregular poly(3-hexylthiophene) (-P3HT) as the conjugated polymeric side chain. To this end, the -norbornenyl-functionalized P3HT macromonomer was synthesized by Kumada catalyst transfer polycondensation (KCTP) followed by postpolymerization modifications, and the resulting conjugated macromonomer was successfully polymerized by ring-opening metathesis polymerization (ROMP) in a controlled manner. The P3HT molecular bottlebrushes display an unprecedented strong physical aggregation upon drying during recovery, as verified by several analyses of the solution and solid states.

Layer-by-layer templated assembly of silica at the nanoscale.

Bioinspired bottom-up assembly and layer-by-layer (LbL) construction of inorganic materials from lithographically defined organic templates enables the fabrication of nanostructured systems under mild temperature and pH conditions. Such processes open the door to low-impact manufacturing and facile recycling of hybrid materials for energy, biology, and information technologies. Here, templated LbL assembly of silica was achieved using a combination of electron beam lithography, chemical lift-off, and aqueous solution chemistry.

Versatility of alkyne-modified poly(glycidyl methacrylate) layers for click reactions.

Functional soft interfaces are of interest for a variety of technologies. We describe three methods for preparing substrates with alkyne groups, which show versatility for "click" chemistry reactions. Two of the methods have the same root: formation of thin, covalently attached, reactive interfacial layers of poly(glycidyl methacrylate) (PGMA) via spin coating onto silicon wafers followed by reactive modification with either propargylamine or 5-hexynoic acid.

Nonfunctionalized polydimethyl siloxane superhydrophobic surfaces based on hydrophobic-hydrophilic interactions.

Superhydrophobic surfaces based on polydimethyl siloxane (PDMS) were fabricated using a 50:50 PDMS-poly(ethylene glycol) (PEG) blend. PDMS was mixed with PEG, and incomplete phase separation yielded a hierarchic structure. The phase-separated mixture was annealed at a temperature close to the crystallization temperature of the PEG.

Polypeptide grafted hyaluronan: synthesis and characterization.

Poly(l-leucine) grafted hyaluronan (HA-g-PLeu) has been synthesized via a Michael addition reaction between primary amine terminated poly(l-leucine) and acrylate-functionalized HA (TBAHA-acrylate). The precursor hyaluronan was first functionalized with acrylate groups by reaction with acryloyl chloride in the presence of triethylamine in N,N-dimethylformamide. (1)H NMR analysis of the resulting product indicated that an increase in the concentration of acryloylchoride with respect to hydroxyl groups on HA has only a moderate effect on functionalization efficiency, f.

Immobilization of biomolecules on poly(vinyldimethylazlactone)-containing surface scaffolds.

We describe the successful development of a procedure for the step-by-step formation of a reactive, multilayer polymer scaffold incorporating polymers based on 2-vinyl-4,4-dimethylazlactone (VDMA) on a silicon wafer and the characterization of these materials. Also discussed is the development of a procedure for the nonsite specific attachment of a biomolecule to a modified silicon wafer, including scaffolds modified via drop-on-demand (DOD) inkjet printing. VDMA-based polymers were used because of their hydrolytic stability and ability of the pendant azlactone rings to form stable covalent bonds with primary amines without byproducts via nucleophilic addition.