Protein adsorption and reversible cell attachment are investigated as a function of the grafting density of poly(N‐isopropyl acrylamide) (PNIPAM) brushes. Prior studies demonstrated that the thermally driven collapse of grafted PNIPAM above the lower critical solution temperature of 32 °C is not required for protein adsorption. Here, the dependence of reversible, protein‐mediated cell adhesion on the polymer chain density, above and below the lower critical solution temperature, is reported. Above 32 °C, protein adsorption on PNIPAM brushes grafted from a non‐adsorbing, oligo(ethylene oxide)‐coated surface exhibits a maximum with respect to the grafting density. Few cells attach to either dilute or densely grafted PNIPAM chains, independent of whether the polymer brush collapses above 32 °C. However, both cells and proteins adsorb reversibly at intermediate chain densities. This supports a model in which the proteins, which support reversible cell attachment, adsorb by penetrating the brushes at intermediate grafting densities, under poor solvent conditions. In this scenario, reversible protein adsorption to PNIPAM brushes is determined by the thermal modulation of relative protein‐segment attraction and osmotic repulsion.

Various ladder‐like structured poly(phenyl‐co‐methacryl silsesquioxane)s (LPMSQ)s with high molecular weight (Mw = 10,000 ∼ 40,000) were synthesized by direct hydrolysis and polymerization in the presence of base catalyst at 25 °C. Synthesized LPMSQs mainly showed ladder‐like structure and photo‐cure reaction by 100 mW/cm2 (360 nm) for 10 s without any photo‐cure initiators. Chemical composition and structural analysis of the obtained LPMSQs were characterized using 1H NMR, 29Si NMR, Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), and X‐ray diffraction (XRD). Physical properties of LPMSQs before and after photcuring were analyzed by Nanoindentation. Surface modulus increased to 8GPa and hardness of thin films increased from 100 to 400 MPa. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

A label free biosensor based upon a vertically emitting distributed feedback ͑DFB͒ laser has been demonstrated. The DFB laser comprises a replica-molded, one-dimensional dielectric grating coated with laser dye-doped polymer as the gain medium. Adsorption of biomolecules onto the laser surface alters the DFB laser emission wavelength, thereby permitting the kinetic adsorption of a protein polymer monolayer or the specific binding of small molecules to be quantified. A bulk sensitivity of 16.6 nm per refractive index unit and the detection of a monolayer of the protein polymer poly͑Lys, Phe͒ have been observed with this biosensor. The sensor represents a departure from conventional passive resonant optical sensors from the standpoint that the device actively generates its own narrowband high intensity output without stringent requirements on the coupling alignments, resulting in a simple, robust illumination and detection configuration.

Through fine-tuning of the myriad of reaction conditions for an aqueous base-catalyzed hydrolysis−polycondensation reaction, a facile synthesis of structurally controlled polyphenylsilsesquioxanes was developed. Mechanism and kinetic studies indicated that the condensation reaction proceeded through a T 1 structured dimer, which was quantitatively and in situ formed through mild hydrolysis of a phenyltrimethoxysilane (PTMS) monomer, to give either the cage-structured polyhedral oligomeric silsesquioxanes (POSS) or the corresponding ladderlike silsesquioxane (LPSQ) with excellent yields. Ladderlike and POSS materials were selectively achieved at higher and lower initial concentrations of PTMS, respectively, and an in-depth spectroscopic analysis of both compounds clearly revealed their structural differences with different molecular weights.