Geometric properties polymers

Sukigara, S., Gandhi, M., Ayutsede, J., Micklus, M., and Ko, F. "Regeneration of Bombyx mori silk by electrospinning - part 1 Processing parameters and geometric properties". Polymer 44(19), 5721-5727 (2003). 

S. Sukigara, M. Gandhi, J. Ayutsede, M. Micklus, F. Ko. 2003. Regeneration of Bombyx mori silk by electrospinning part FProcessing Parameters and Geometric Properties. Polymer, 44.pp. 5721-5727. 

Lyons J, Li C, Ko F (2004) Melt-electrospinning part I processing parameters and geometric properties. Polymer 45 7597-7603... 

The geometric properties of highly denatured states appear to be consistent with those expected for a random-coil polymer. For example, proteins unfolded at high temperatures or in high concentrations of denaturant invariably produce Kratky scattering profiles exhibiting the monotonic increase indicative of an expanded, coil-like conformation (Fig. 1) (Hagihara et al., 1998 see also Doniach et al., 1995). Consistent... 

Geometric Examination. The polymer chemist needs to examine the various characteristics of the molecule in the molecular workspace. Bond lengths, bond angles and torsional angles can be measured for the current structure and compared to accepted values. In addition, other geometric properties can be computed like overall dimension, moments of inertia, molecular volume and surface area. 

S. D. Stellman and P. J. Cans, Macromolecules, 5, 516 (1972). Efficient Computer Simulation of Polymer Conformation. 1. Geometric Properties of the Hard-Sphere Model. 

The study of hydrodynamic properties (sedimentation, diffusion and viscosity) of dilute polymer solutions is the most widely used method permitting the characterization of geometric properties (size and conformation) of polymer molecules. 

Any flexible polymer adsorbing to a solid/liquid interface must (1) be transported from the solution towards the surface, (2) establish a sufficient number of attachment points, and (3) change its conformation to achieve the state of lowest Gibbs energy, by accommodating to the geometrical properties of the substrate [1]. 

In an earlier section, we discussed molecular chains with continuous curvature. These models enable one to st udy polymer conformational structure by means of notions of elasticity theory. As seen, geometrical properties (e.g., curvature, torsion, twist, writhe) and topological properties (e.g., linking) can be used to characterize the molecular shapes of ID models. This approach can be generalized to the study of 2D elastic surfaces. 

Despite its unquestionable importance, the macromolecular coil fractal dimension Dj gives only limited information about an aggregation (polymerization) process. Firstly it is a static value and does not describe the dynamics of an aggregation process. Secondly, the dimension characterizes geometrical properties of otdy one cluster (macromolecular coil) and cannot be used for the description of a set of clusters [99]. Thus, both classical and fractal approaches indicate the need for polymers MWD study for their characteristic completeness. 

The investigation of hydrodynamic properties, sedimentation and translational and rotational friction of dilute solutions, of these polymers using modern theoretical concepts of behavior of macromolecules in solution made it possible to characterize the geometric properties of macromolecules, their size and equilibrium rigidity. 

So far as the geometrical properties are concerned, we first note the ladi of transla tional invariance for a particular realization of disorder and therefore (r) 0, but on averaging over randomness, translational invariance will be restored statistically and so [(r)] has to be zero. One may therefore consider the size of the polymer by the disorder correlations... 

Paths are conceived as lines in a geometric space. In a simple way, the geometry of a path is expressed as the relation between its length and its end-to-end distance. An abstract path assumes a concrete form when it is associated with a physical object, for example, the trail of a moving particle, the course of a river, the configuration of a linear polymer and the contour of a domain. Optimal paths and most probable paths are two classes of such concrete forms. While optimal paths are defined for zero temperature and are always self-avoiding, most probable paths are defined in the thermodynamic sense for all temperatures and may have self-intersections. This is a review of the geometric properties of optimal and most probable paths on lattices with randomly disordered bonds it contains a brief description of the methods used to study these paths and the main characteristics of their forms. 

Proposals were made by a series of publications to fabricate MD membranes using SMMs. Khayet and Matsuura (2001) prepared PVDF flat-sheet membranes for MD. They used pure water as a pore-fonning additive in the casting solution, while dimethylacetamide (DMAc) was used as the solvent. Their polymer solutions were cast over a glass plate or over a nonwoven polyester backing material. They characterized the prepared supported and unsupported PVDF membranes in terms of nonwettability, pore size, and porosity. The prepared membranes were tested in VMD experiments for the separation of chloroform from a chloroform/water solution. They have also studied the dependence of the MD flux and the separation factor on the geometrical properties of the supported and unsupported membranes. 

To conclude, it is believed that ab initio quantum chemistry methods in the spirit of the approach presented in this paper will play an increasing role in the investigation of structural and geometrical properties of polymer glasses. They provide tools for quantitative analysis of NMR spectra to yield structural information on a strictly local length scale. Solid state NMR can thus complement the scattering methods which probe the samples mainly at greater distances. 

Highly ordered cylindrical monolayer conformations of adsorbed polymers with different wrappings in the barrel phase B at 6f = 5 for (a) at = 1.50, (b) at = 1.57, and (c) af = 0.65 (different shadings shall fecilitate the perception only). Geometric properties of these structures resemble chiral alignments of atomic structures known from single-walled nanotubes. From [321]. 

The flow of material in twin-screw extruders is very complex, and the flow patterns are difficult to predict mathematically. For this reason the simulation of processes in twin-screw extruders is not as well developed as it is for single-screw extruders. It is therefore difficult to predict the performance of a twin-screw extruder based on geometrical features, polymer properties, and processing conditions. Hence, it is difficult to carry out accurate design calculations. For this reason twin-screw extruders are constructed... 

The radiation and temperature dependent mechanical properties of viscoelastic materials (modulus and loss) are of great interest throughout the plastics, polymer, and rubber from initial design to routine production. There are a number of laboratory research instruments are available to determine these properties. All these hardness tests conducted on polymeric materials involve the penetration of the sample under consideration by loaded spheres or other geometric shapes [1]. Most of these tests are to some extent arbitrary because the penetration of an indenter into viscoelastic material increases with time. For example, standard durometer test (the "Shore A") is widely used to measure the static "hardness" or resistance to indentation. However, it does not measure basic material properties, and its results depend on the specimen geometry (it is difficult to make available the identity of the initial position of the devices on cylinder or spherical surfaces while measuring) and test conditions, and some arbitrary time must be selected to compare different materials. 

The value of many chemical products, from pesticides to pharmaceuticals to high performance polymers, is based on unique properties of a particular isomer from which the product is ultimately derived. Eor example, trisubstituted aromatics may have as many as 10 possible geometric isomers whose ratio ia the mixture is determined by equiHbrium. Often the purity requirement for the desired product iacludes an upper limit on the content of one or more of the other isomers. This separation problem is a compHcated one, but one ia which adsorptive separation processes offer the greatest chances for success. 

With the exception of glass fiber, asbestos (qv), and the specialty metallic and ceramic fibers, textile fibers are a class of soHd organic polymers distinguishable from other polymers by their physical properties and characteristic geometric dimensions (see Glass Refractory fibers). The physical properties of textile fibers, and indeed of all materials, are a reflection of molecular stmcture and intermolecular organization. The abiUty of certain polymers to form fibers can be traced to several stmctural features at different levels of organization rather than to any one particular molecular property. 

Other minor raw materials are used for specific needs. Eumaric acid [110-17-8] the geometric isomer of maleic acid, is selected to maximize thermal or corrosion performance and is the sole acid esterified with bisphenol A diol derivatives to obtain optimum polymer performance. CycloaUphatics such as hydrogenated bisphenol A (HBPA) and cyclohexanedimethanol (CHDM) are used in selective formulations for electrical apphcations. TetrahydrophthaUc anhydride [85-43-8] (THPA) can be used to improve resiUence and impart useful air-drying properties to polyester resins intended for coating or lining apphcations. 

Cycloahphatic diamines which have reacted with diacids to form polyamides generate performance polymers whose physical properties are dependent on the diamine geometric isomers. (58,74). Proprietary transparent thermoplastic polyadipamides have been optimized by selecting the proper mixtures of PDCHA geometric isomers (32—34) for incorporation (75) ... 

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