Number Of Methylene Carbons Research Articles

Molecular Dynamics Study on the Water Mobility and Side-Chain Flexibility of Hydrated Poly(ω-methoxyalkyl acrylate)s.

Intermediate water (IW) is known to play an important role in the antifouling property of biocompatible polymers. However, how IW prevents protein adsorption is still unclear. To understand the role of IW in the antifouling mechanism, molecular dynamics simulation was used to investigate the dynamic properties of water and side-chains for hydrated poly(ω-methoxyalkyl acrylate)s (PMCxA, where x indicates the number of methylene carbons) with x = 1-6 and poly(n-butyl acrylate) (PBA) in this study. Since the polymers uptake more water than their equilibrium water content (EWC) at the polymer/water interface, we analyzed the hydrated polymers at a water content higher than that of EWC. It was found that the water molecules interacting with one polymer oxygen atom (BW1), of which most are IW molecules, in PMC2A exhibit the lowest mobility, while those in PBA and PMC1A show a higher mobility. The result was consistent with the expectation that the biocompatible polymer with a long-resident hydration layer possesses good antifouling property. Through the detailed analysis of side-chain binding with three different types of BW1 molecules, we found that the amount of side-chains simultaneously interacting with two BW1 molecules, which exhibit the highest flexibility among the three kinds of side-chains, is the lowest for PMC1A. The high mobility of BW1 is thus suggested as the main factor for the poor protein adsorption resistance of PMC1A even though it possesses enough IW content and relatively flexible side-chains. Contrarily, a maximum amount of side-chains simultaneously interacting with two BW1 molecules was found in the hydrated PMC3A. The moderate side-chain length of PMC3A allows side-chains to simultaneously interact with two BW1 molecules and minimizes the hydrophobic part attractively interacting with a protein at the polymer/water interface. The unique structure of PMC3A may be the reason causing the best protein adsorption resistance among the PMCxAs.

Elucidating the Feature of Intermediate Water in Hydrated Poly(ω-methoxyalkyl acrylate)s by Molecular Dynamics Simulation and Differential Scanning Calorimetry Measurement.

Intermediate water (IW) has been reported to play an important role in nonthrombogenicity of biomaterials. However, clear insights into the IW in the hydrated polymer are still debated. In this study, a series of molecular dynamics simulations was performed to identify the IW structure in hydrated poly(ω-methoxyalkyl acrylate)s (PMCxAs, where x indicates the number of methylene carbons) with x = 1-6. Through the quantitative comparison with experimental measurements, IW molecules were suggested to mainly come from the water interacting with an oxygen atom of the polymers, while most of the nonfreezing water (NFW) molecules corresponded to the water interacting with two polymer oxygen atoms. In addition, the IW molecules were found to effectively enhance the flexibility of the PMCxA side chains in comparison with the NFW molecules. The variations of the saturated IW content and the side-chain flexibility with the methylene carbon chain length of PMCxA were also found to be correlated with the experimental nonthrombogenicity of PMCxA, suggesting that the polymer with the more saturated IW content and higher chain flexibility possesses better nonthrombogenicity. Furthermore, through the analyses of the interplays between the IW and polymer and between IW and its adjacent water, we found that the presence of the unique interaction between IW and its adjacent water in the hydrated poly(2-methoxyethyl acrylate) (PMEA) is the main factor causing different cold crystallization behaviors of PMEA from the other PMCxAs rather than the interaction between water and the PMCxA matrix. The findings will be useful in the development of new nonthrombogenic materials.

Cooperative Binding and the Conformation of Poly(l-Glutamic Acid) in Guanidinium Salts with an Alkanoylamidoalkyl Group

We investigated the change in the conformation of poly(l-glutamic acid) from a random coil to an α-helix in solutions of guanidinium salts with a dodecanoylamidoalkyl group, C12AmG (m = 0, 2, 3, 4, 6), where Am indicates a methylene spacer between the dodecanoyl group and guanidine and m is the number of methylene carbons. C12AmGs (m = 0, 2, 3, 4) induced an α-helix in P(Glu), but C12A6G failed. Binding isotherms were constructed from the potentiometry of bound C12AmG and cooperative binding was observed, as found in many regular surfactants. All C12AmG gave a similar cooperative parameter and overall binding constants of comparative order (113 × 103 to 255 × 103). In contrast to the methylene group in regular surfactants, the methylene spacer in C12AmG had a minor effect on hydrophobic interactions. C12A0G showed the strongest cooperative binding and effect on the formation of the α-helix in P(Glu). The methylene spacer interfered with C12AmG binding and α-helix formation in P(Glu).

Inhibiting Effects of Lunularic Acid Analogs on the Growth of Liverwort, Watercress, and Timothy Grass

A number of analogs of lunularic acid varying in the number of methylene carbons between the two benzene rings and in the substituents on their rings were prepared, and their effects on the growth of liverwort gemmaling, watercress, and timothy grass were investigated. Almost all the analogs tested were more inhibitory than lunularic acid, and a correlation between the structure and activity was observed. The differences in the growth-inhibition activity of analogs between higher and lower plants are also discussed.

Comparative study of the interaction of ‘lop-sided’ 14- to 17-membered tetraaza macrocycles containing fused dibenzo substituents with nickel(II)

The effect of macrocyclic and chelate-ring size on the complexation behaviour of a series of dibenzo tetraaza macrocycles incorporating 14- to 17-membered inner rings has been investigated. Change in ring size along this ‘lop-sided%’ series has been achieved solely by varying the number of methylene carbons that link adjacent benzyl nitrogen atoms. Several solid complexes of type NiLX2·xH2O (L = macrocyclic ligand; x= 0 or 1; X = Cl, NCS or NO3) with these rings have been isolated. The results of five X-ray crystallographic analyses, as well as molecular mechanics studies, have allowed comparison of the effect of change of ring size on the structures of the 14- to 17-membered ring complexes with X = NCS. All complexes have similar six-co-ordinate trans-isothiocyanato geometries in which the four donors of the macrocycle occupy the equatorial plane. For this series an inverse correlation between in-plane and axial bond lengths around the nickel atoms occurs for the 14- to 16-membered ring complexes; the correlation is less apparent in the case of the 17-membered species. The X-ray and molecular mechanics studies indicate that, as the number of methylene carbons linking adjacent benzylamino nitrogens increases, the corresponding bite angle at the metal increases, with the opposite bite angle decreasing in a (partial) compensatory manner. As a consequence, there is only a minor variation in the planarity of the macrocyclic donor plane along the series. The crystal structure of the 16-membered ring complex of nickel(II) nitrate is also reported, as is that of the 17-membered ring complex of nickel(II) chloride. The former contains an equal mixture of two (trans-octahedral) complexes of type [NiL(NO3)2] and [NiL(NO3)(H2O)]NO3. Cyclic voltammetry indicates that formation of the respective nickel(III) species is facilitated by the smaller-ring ligands; the oxidation of the 17-membered ring complex is non-reversible and probably ligand based.

Chain‐extended polyurethanes—Synthesis and characterization

AbstractThermoset polyurethane (PU) elastomers were prepared using hydroxyl‐terminated polybutadiene (HTPB), toluene diisocyanate (TDI) and hexamethylene diisocyanate (HMDI). The effects of various diamines and diols on the mechanical and thermal properties of polyurethanes are discussed. The average molecular weight between crosslinks (M̄/c) was determined by swelling studies. The properties imparted by the extenders are explained on the basis of the groups present in the diamines and the number of methylene carbons in the diols.

Cast Polyurethanes: Effect of Chain Extenders on Thermal Mechanical and Dynamic Mechanical Properties

Abstract Effects of various diol chain extenders on thermal, mechanical, and viscoelastic properties of polyurethanes are discussed. Elastomers were prepared by using polyester (polyethylene-co-propylene adipate), toluene-2,4-diisocyanate, and α,ω-aliphatic diols. The properties imparted by the extenders are explained on the basis of the number of methylene carbons in the extenders. Butanediol-extended polymer showed superior properties, which are ascribed to regularity in the backbone chain of the polymer and ease of formation of hydrogen bonds.

The determination of the elastic constants of a series of n-alkylcyanobiphenyls by anisotropy of turbidity

Measurement of the anisotropy of turbidity of aligned nematic liquid crystals in three selected geometries can yield the splay, twist, and bend elastic constants (K11, K22, and K33, respectively) which, along with the viscosity coefficients of the medium, govern director fluctuations that lead to a strong light scattering. We have utilized this procedure to determine the temperature dependence of the elastic constants of a homologous series of n-alkycyanobiphenyls (n-CB, where n=5, 6, 7, 8) in the nematic range. K33≳K11≳K22 at all temperatures for each member of the series. The absolute values of the moduli are consistently higher than those obtained by magneto- and electro-optic distortion methods (Frederik’s transitions). Odd–even effects are displayed as the number of methylene carbons in the alkyl chain increases. Distinctly larger K33 values for 8CB may be attributed to the short range smectic ordering in this liquid crystal, which has a lower temperature smectic-A phase.

Crosslinking and Mechanical Properties of Liquid Rubber. I. Curative Effect of Aliphatic DIOLS

Abstract The structure-property relationships of polyurethane elastomers derived from a liquid hydroxyl-terminated polybutadiene/low molecular weight aliphatic diol/diisocyanate system were studied. The effects of the amount of low molecular weight diol on the mechanical properties of the elastomer were discussed on the basis of the results of stress-strain, swelling, dynamic viscoelasticity, x-ray diffraction, etc. It was found that some particular combinations of low molecular weight diol and diisocyanate specifically affect the properties of elastomers. When the mechanical properties of the elastomers were plotted against the number of methylene carbons in the low molecular weight diol, characteristic zigzag patterns were obtained. These patterns were explained by the difference in the packing and the dependence of the strength of intermolecular hydrogen bonding on whether the number of the methylene carbons was even or odd. This assumption was confirmed by x-ray diffraction.

Crosslinking and mechanical property of liquid rubber. I. Curative effect of aliphatic diols

AbstractThe structure–property relationships of polyurethane elastomer derived from liquid hydroxylterminated polybutadiene/low molecular weight aliphatic diol/diisocyanate system were studied. The effects of the amount of low molecular weight diol on the mechanical properties of elastomer were discussed on the basis of the results of the stress–strain curve, swelling, dynamic viscoelasticity, x‐ray diffraction, and others. It was found that some particular combinations of low molecular weight diol and diisocyanate specifically affect the properties of elastomers. When the mechanical properties of the elastomers were plotted against the number of methylene carbons in low molecular weight diol, the characteristic zigzag patterns were obtained. These patterns were explained by the difference in the packing and the dependence of the ability of intermolecular hydrogen bonding on whether the number of the methylene carbons was even or odd. This assumption was confirmed by x‐ray diffraction.