Semi-flexibility

One model for rod-like colloids is tire tobacco mosaic vims (TM V), which consists of rods of diameter D about 18 nm and lengtli L of 300 nm [17,18]. These colloids have tire advantage of being quite monodisperse, but are hard to obtain in large amounts. The fd vims gives longer, semi-flexible rods (L = 880 nm, D = 9 nm) [18,19]. Inorganic boehmite rods have also been prepared successfully [20]. 

Commonly used isocyanates are toluene dhsocyanate, methylene diphenyl isocyanate, and polymeric isocyanates. Polyols used are macroglycols based on either polyester or polyether. The former [poly(ethylene phthalate) or poly(ethylene 1,6-hexanedioate)] have hydroxyl groups that are free to react with the isocyanate. Most flexible foam is made from 80/20 toluene dhsocyanate (which refers to the ratio of 2,4-toluene dhsocyanate to 2,6-toluene dhsocyanate). High-resilience foam contains about 80% 80/20 toluene dhsocyanate and 20% poly(methylene diphenyl isocyanate), while semi-flexible foam is almost always 100% poly(methylene diphenyl isocyanate). Much of the latter reacts by trimerization to form isocyanurate rings. 

The RIM process was originally developed for the car industry for the production of bumpers, front ends, rear ends, fascia panels and instrument housings. At least one mass-produced American car has RIM body panels. For many of these products, however, a number of injection moulding products are competitive, including such diverse materials as polycarbonate/PBT blends and polypropylene/EPDM blends. In the shoe industry the RIM process has been used to make soling materials from semi-flexible polyurethane foams. 

The changes in the average chain length of a solution of semi-flexible selfassembling chains confined between two hard repulsive walls as the width of the sht T> is varied, have been studied [61] using two different Monte Carlo models for fast equihbration of the system, that of a shthering snake and of the independent monomer states. A polydisperse system of chain molecules in conditions of equilibrium polymerization, confined in a gap which is either closed (with fixed total density) or open and in contact with an external reservoir, has been considered. 

G. I. Menon, R. Pandit, M. Barma. Melts of semi-flexible, living polymers A lattice model. Europhys Lett 24 253-258, 1993. 

J. S. Pedersen, M. Laso, P. Schurtenberger. Monte Carlo study of excluded volume effects in worm-like micelles and semi-flexible polymers. Phys Rev E 54 R5917-R5920, 1996. 

Semi-flexible Coupling Protects Drive Equipment and Pressure Seols... 

Semi-Flexible Chains Worm-Like Cods. 241... 

Semi-flexible coil cellulose derivatives, chitosans... 

The rheological behaviour of polymeric solutions is strongly influenced by the conformation of the polymer. In principle one has to deal with three different conformations, namely (1) random coil polymers (2) semi-flexible rod-like macromolecules and (2) rigid rods. It is easily understood that the hydrody-namically effective volume increases in the sequence mentioned, i.e. molecules with an equal degree of polymerisation exhibit drastically larger viscosities in a rod-like conformation than as statistical coil molecules. An experimental parameter, easily determined, for the conformation of a polymer is the exponent a of the Mark-Houwink relationship [25,26]. In the case of coiled polymers a is between 0.5 and 0.9,semi-flexible rods exhibit values between 1 and 1.3, whereas for an ideal rod the intrinsic viscosity is found to be proportional to M2. 

The molecule is either fully flexible or semi-flexible. The fully flexible chains are generally harder to crystallize than semi-flexible chains [35]. In the latter part of the paper (Sect. 5), where we discuss crystallization from the melt, we consider a semi-flexible chain, the flexibility of which is adjusted to reproduce the characteristic ratio of real polyethylene. We there make the... 

The polymer we consider here is a semi-flexible chain which has some bending stiffness (Eq. 3). We first estimated the chain conformation in the melt. The calculated mean-square end-to-end distance R2n between atoms n-bond apart has shown that the chains have an ideal Gaussian conformation R2 is a linear function of n (see Fig. 35 given later). The value of R2 for n = 100... 

The transitions of the coil-globule type were considered not only in the usual space, but also in the space of monomeric units orientation, where such transition is equivalent to the nematic liquid crystal ordering [60,61]. Such an approach using the formalism developed by I.M. Lifshitz has led to the creation of the theory of liquid crystal ordering in the solutions of semi-flexible macromolecules [62,63]. 

Dendrimers within a generational series, can be expected to present their terminal groups in at least three different modes, namely flexible, semi-flexible or... 

For a semi-flexible tube in a dilute environment, local repulsive potentials among parts of the fiber induce a self-avoiding random walk configuration (swollen coil [151]). In a crowded environment, the depletive action may dominate and the fiber will tend to collapse on itself, forming a globular phase. We know from standard statistical physics of polymers that this latter phase... 

The flexible, semi-flexible, or anancomeric behavior of tetrahydro-l,3-oxazines 83 spiro-connected to cyclohexane was studied by NMR spectroscopy. The possible stereoisomers were deduced by taking into account the special chirality of the heterocycle and the spiro skeleton <2000M975>. 

The connecting of the movable parts (hlters) can be executed with semi-flexible metallic ducts. Their lengths must be as short as possible. 

Semi-flexible SUDICRETE formulations have strong potential for road paving applications. Though still in the development phase, the materials have shown very high resistance to fatigue damage. 

The engineering properties of Sulphlex binders when combined with mineral aggregates are similar to those for paving materials. As such, the principal application may be in pavements, either semi-flexible or rigid, depending on the formulation used. 

We turn now to the other major whey protein, p-lactoglobulin. This is an acidic globular protein (p/= 5.1) with a molar mass of 18.4 kDa and a radius of about 2 nm (Aymard et al., 1999). The protein can form long semi-flexible fibrils when heated in solution at around or above its dena-turation temperature (60-80 °C) at pH = 2 and low ionic strength (Durand et al., 2002 Veerman et al., 2002, 2003a,b). (An example of the... 

Sagis, L.M.C., Veennan, C., van der Linden, E. (2004). Mesoscopic properties of semi-flexible amyloid fibrils. Langmuir, 20, 924-927. 

Flory, P. J. Statistical thermodynamics of semi-flexible chain molecules. Proc. Roy. Soc. (London) A234,60-73 (1956). 

The structural semi-flexible and rigid urethane foams, combining high strength with low density and low cost, have found wide interest and early acceptance in divergent markets although this development is still quite new. The semi-flexible foams are used primarily in the transportation industry. At medium densities,... 

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