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Kinetics and its regulation by extrinsic physical factors govern selectin–ligand interactions that mediate tethering and rolling of circulating cells on the vessel wall under hemodynamic forces. While the force regulation of off-rate for dissociation of selectin–ligand bonds has been extensively studied, much less is known about how transport impacts the on-rate for association of these bonds and...
Single-molecule force spectroscopy, especially as implemented on an atomic force microscopy (AFM) platform is unique in its ability to apply small (F<10pN) and large (F>1000pN) stretching forces to individual polymer chains and in this way examines their elasticity and also reports force-induced conformational transitions in whole polymers and in their building blocks. In this paper, we briefly...
We investigated various stimuli-responsive poly(ferrocenylsilane) (PFS) polymers as model systems for the realization of molecular motors powered by a redox process. Covalently end-grafted PFS on gold, as well as PFS homopolymers and block copolymers in ultrathin films, were studied by AFM-based single molecule force spectroscopy (SMFS). Surface confined PFS macromolecules were chemically oxidized...
A new diamine monomer containing noncoplanar methyl substitution, 2,2′-dimethyl-4,4′-bis(2-trifluoromethyl-4-aminophenoxy)biphenyl (DBTFAPB) was successfully synthesized and used in the preparation of a series of polyamides and polyimides by direct polycondensation with various aromatic dicarboxylic acids and tertacarboxylic dianhydrides. A new noncoplanar dicarboxylic acid monomer containing noncoplanar...
Microrheology was employed to perform in situ monitoring of the liquid-to-gel transition during free-radical photopolymerization. Photosensitive acrylate resins were exposed to ultraviolet light, while the Brownian motion of micrometer sized, inert fluorescent tracer particles was tracked via optical videomicroscopy. Statistical analysis of particle motion yielded the rheological properties of the...
The fracture behavior of composite rubber particle-toughened polymethylmethacrylate has been investigated over a wide range of test speeds, encompassing impact conditions. When the entanglement density of the matrix was increased and its glass transition temperature reduced by copolymerization, there were significant increases in the crack initiation and propagation resistance of the particle-toughened...
Holographic polymer dispersed liquid crystals (HPDLCs) are targeted for application in a wide range of devices as dynamically switchable transmission or reflection diffraction gratings tunable through the visible spectra. The inclusion of N-vinyl pyrrolidinone (NVP) has been shown to reduce liquid crystal (LC) droplet size in HPDLC gratings and subsequently improve HPDLC performance. In this work,...
A method, which is called as ‘nanofishing’, enabled us to stretch a single polymer chain adsorbed on an Au(111) substrate with picking it at its two thiol-modified termini using atomic force microscope equipped with a gold-coated probe. A force–extension curve obtained for a single polystyrene chain in a Θ solvent (cyclohexane) showed a good agreement with a so-called worm-like chain model, and thus...
4-Vinylbenzyl glucoside peracetate (1) was copolymerized with divinylbenzene (DVB) using 1-phenyl-1-(2′,2′,6′,6′-tetramethyl-1′-piperidinyloxy)ethane (2) as an initiator in m-xylene at 138°C for 20h ([DVB]/[2]=28; [DVB]=0.62molL −1 ). The copolymerizations were performed using the mole fraction of 1 in the total feed of 1 and DVB (F 1 : [1]/[1]+[DVB]) ranging from 0.11 to 0.38 that...
Tenascin, an important extracellular matrix protein, is subject to stretching force under physiological conditions and plays important roles in regulating the cell–matrix interactions. Using the recently developed single molecule force–ramp spectroscopy, we investigated the unfolding–folding kinetics of a recombinant tenascin fragment TNfnALL. Our results showed that all the 15 FnIII domains in TNfnALL...
Using single molecule force spectroscopy (SMFS), we have investigated the single chain elasticity of a series of dendronized copolymers, whose original backbone is styryl dendron and maleic anhydride. The amilysis reaction of maleic anhydride introduces amide and carboxyl side groups. Hence, the copolymer bears three type side groups, Fréchet type dendrons, amides and carboxyls. The single chain elasticity...
Polymers play a central role in cantilever-based single molecule force spectroscopy, either as sample or as anchor of the molecular complexes under investigation. Here we investigated the role of the polymer for the coupling of thermal and mechanical fluctuations of the cantilever into the molecular complex under investigation. We first analyzed the low pass characteristics of the polymeric anchor...
A study on the correlation between electrical percolation and viscoelastic percolation for graphite (GP) filled high-density polyethylene (HDPE) conductive composites was carried out through an examination of the filler concentration φ dependence of the volume resistivity ρ and dynamic viscoelastic functions. The frequency ω dependence of G′ at low ωs decreased obviously with increasing GP concentration...
An interfacial polymerization method for nylon 6,6 was adapted to produce nanocomposites with single wall carbon nanotubes (SWNT) via in situ polymerization. SWNT were incorporated in purified, functionalized or surfactant stabilized forms. The functionalization of SWNT was characterized by FTIR, Raman spectroscopy and TGA and the SWNT dispersion was characterized by optical microscopy before and...
In crowded solutions the presence of many cosolutes often affects the stability of compact polymers, such as globular proteins. Important examples of crowded environments are those inside some cells, where protein stability or aggregation rates are affected by the presence of co-existing bio-macromolecules. In the present article the concept of depletion force from colloidal physics and theoretical...
Cinnamate polymers are well known photoreactive polymers due to [2+2] cycloaddition reaction of cinnamate side group. In this work, we have found that the cinnamate side groups could be also reacted by thermal energy, and this reaction is presumed to attribute to the radical reaction of carbon double bond in the cinnamate groups. Contrary to the photocycloaddition reaction of the cinnamate side groups,...
The orientation of polymer chain has a great effect on its mechanical properties, therefore, it is always an important issue on how to characterize, accurately and quickly, the orientation of polymer chain during processing. In this article, according to the property that ultrasound travels in different velocities in anisotropic media, normal incident shear wave was utilized to explore the orientation...
Superparamagnetic functional carriers to obtain high selectivity were reported in this study. Magnetic carriers with epoxy groups were synthesized by spraying suspension polymerization (SSP). The measurement of scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM) showed that the magnetic carriers have a narrow size distribution and displayed superparamagnetic characteristics...
We report a study of the impact of cold crystallization on the structure of nanocomposites comprising poly(vinylidene fluoride) (PVDF) and Lucentite STN™ organically modified silicate (OMS). Nanocomposites were prepared from solution over a very wide composition range, from 0.01 to 20% OMS by weight. Thermal preparation involved cold crystallization at 145°C of quenched, compression-molded plaques...
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