Contribution of entanglements to the modulus of end-linked poly(ethylene oxide) networks

Poly(ethylene oxide) networks were made at 75 °C by end-linking of short linear chains with an excess of Tolonate HDT, a tri-functional aliphatic isocyanate. Molecular weights of poly(ethylene oxide)were 4000, 6000 and 12000. The observed elastic moduli were much higher than predicted from affine theory, indicating a large contribution from entanglements in contrast to the findings of previous studies. With increasing excess of cross-linker, the contribution from entanglements levels off at a value of approximately 5 MPa which is in good agreement with the rubber plateau modulus of pure poly(ethylene oxide).     

HPMA‐Based Nanocarriers for Effective Immune System Stimulation

The selective activation of the immune system using nanoparticles as a drug delivery system is a promising field in cancer therapy. Block copolymers from HPMA and laurylmethacrylate‐co‐hymecromone‐methacrylate allow the preparation of multifunctionalized core‐crosslinked micelles of variable size. To activate dendritic cells (DCs) as antigen presenting cells, the carbohydrates mannose and trimannose are introduced into the hydrophilic corona as DC targeting units. To activate DCs, a lipophilic adjuvant (L18‐MDP) is incorporated into the core of the micelles. To elicit an immune response, a model antigen peptide (SIINFEKL) is attached to the polymeric nanoparticle—in addition—via a click reaction with the terminal azide. Thereafter, the differently functionalized micelles are chemically and biologically characterized. While the core‐crosslinked micelles without carbohydrate units are hardly bound by DCs, mannose and trimannose functionalization lead to a strong binding. Flow cytometric analysis and blocking studies employing mannan suggest the requirement of the mannose receptor and DC‐SIGN for effective micelle binding. It could be suppressed by blocking with mannan. Adjuvant‐loaded micelles functionalized with mannose and trimannose activate DCs, and DCs preincubated with antigen‐conjugated micelles induce proliferation of antigen‐specific CD8+ T cells.     

Jet Cross Sections in e+e− Annihilation

Using an elaborate partial fractioning procedure of all 4-parton matrix elements we calculate 3-jet cross sections in e⁺e⁻ annihilation with mass-cut jet resolution. All subleading contributions from nonsingular terms are included. We give thrust distributions for O(α_s²) 3- and 4-jets. We study integrated cross sections as a function of the cutoff and check the reconstruction of O(α_s²) σ_tot using recently calculated 2-jet cross sections with the same partial fractioning of 4-parton terms.     

Characterization of conformational adsorbate changes on a tissue-derived substrate using Fourier transform infrared spectroscopy

Fourier transform infrared (FT-IR) spectroscopy is utilized to observe adsorbate interactions with a tissue-derived collagen scaffold extracted from the Bruch's membrane of pig eyes. The characterization includes conformational changes in isoleucine, polyisoleucine, collagen-binding peptide, RGD-tagged collagen-binding peptide, and laminin after adsorption onto the substrate. Isotopically labeled isoleucine is further utilized to understand changes in the biomolecular structure upon binding to a tissue-derived surface. The adsorbates associated with the collagen scaffold predominately through hydrophobic interactions and hydrogen bonding. The results of this study can be used to improve our understanding of surface chemistry changes during the engineering of biomimetic scaffolds before and after biomolecule adsorption.     

Processing-structure-mechanical property relationships of semicrystalline polyolefin-based block copolymers

The incremental plastic deformation of the crystals of block copolymers made of semicrystalline polypropylene endblocks and amorphous ethylene-r-propylene midblocks occurring during step cycle tensile tests has dramatic effects on the stress-strain curves. This can be understood from the evolution of the morphology and of the microstructure of the crystalline blocks revealed by X-ray scattering experiments. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1428–1437, 2010     

Structural inhomogeneity of interfacial water at lipid monolayers revealed by surface-specific vibrational pump-probe spectroscopy

We report vibrational lifetime measurements of the OH stretch vibration of interfacial water in contact with lipid monolayers, using time-resolved vibrational sum frequency (VSF) spectroscopy. The dynamics of water in contact with four different lipids are reported and are characterized by vibrational relaxation rates measured at 3200, 3300, 3400, and 3500 cm(-1). We observe that the water molecules with an OH frequency ranging from 3300 to 3500 cm(-1) all show vibrational relaxation with a time constant of T(1) = 180 ± 35 fs, similar to what is found for bulk water. Water molecules with OH groups near 3200 cm(-1) show distinctly faster relaxation dynamics, with T(1) < 80 fs. We successfully model the data by describing the interfacial water containing two distinct subensembles in which spectral diffusion is, respectively, rapid (3300-3500 cm(-1)) and absent (3200 cm(-1)). We discuss the potential biological implications of the presence of the strongly hydrogen-bonded, rapidly relaxing water molecules at 3200 cm(-1) that are decoupled from the bulk water system.     

Synthesis of MSn(OH)<Subscript>6</Subscript> (where M = Mg,Ca, Zn,Mn, or Cu) materials at room temperature

Applying a metathesis approach (MCl₂·xH₂O+Na₂SnO₃·xH₂O→MSn(OH)₆+NaCl+xH₂O), Schoenfliesite-type materials with general formula MSn(OH)₆ (where M=Ca, Cu, Mg, Mn or Zn) were synthesized at room-temperature. The high lattice-energy of the by-product alkali halide NaCl drives the reaction in the forward direction leading to the formation of the desired materials. The materials synthesized were characterized by powder X-ray diffraction (XRD) and scanning electron microscopy (SEM) to elucidate structural and micro structural features.