Influence of molecular weight

The conjugation length of oligo(thiophene) increases with the length of the jt-electron system [84]. The absorption maxima of oligo(thiophene)s in CHCI3 

The overall crystallization kinetics of the high molecular weight n-alkanes yields superposable, classical isotherms of the Avrami type. An example is given in Fig. 9.73, where ln(l - X(t)) is plotted against In t for Ci92H3g6.(278) The studied temperature interval of 118-124 °C encompasses the time scale of about 0.25-200 min for the detection of crystallinity. Low frequency Raman acoustical mode (LAM) studies indicate that extended chain crystallites are formed at all temperatures in 

The nature of the interfacial structure of the folded n-alkane crystallites will be discussed in Volume 3. Different possible structures will be presented. At this point it is not necessary to assume either that the crystalUte thickness is quantized or that the interface is sharp with adjacent re-entry.(275,276) Otha- possibilities exist.(277) 

The temperature dependence of the overall crystallization rate is of particular interest in terms of the nucleation processes involved. The log of the crystallization rates for the high molecular weight n-alkanes C168H338, C192H386 and C240H482 are plotted against the crystallization temperature in Fig. 9.75.(280) In this example. 

Results of a similar type of study with C246H494 are given in Fig. 9.76.(281) Here the rate is plotted against the crystallization temperature. The rate displays a maximum, followed by a sharp minimum. A rapid increase in the rate then occurs over a very narrow temperature region. Similar results have been reported for normal hydrocarbons ranging from C194H390 to C294H590. (282) The plots in Fig. 9.75 imply a similar behavior. The observation of a rate maximum in the vicinity of is a unique 

Crystallization kinetics of homopolymers Table 9.9. Slopes of straight lines in Fig. 9.77 

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Figure 16.8. Influence of molecular weight on the tensile strength of polystyrene...

Fig. 10 SEM of nanoporous PS materials showing the influence of molecular weight on the ordering of templates a 67 kg mol-1 b 132kgmoF1 c pore diameter histograms. Reproduced from [39]...

Figure 6.10 Influence of molecular weight on the adsorption of polyethyleneimines (PEI) by a bleached sulfite pulp (PEI 10 = DP of 10 and PEI 500 = DP 500).

Pressure Dependence of the Segmental Relaxation of Polybutadiene and Polyisobutylene and Influence of Molecular Weight. 

The concept of chain entanglements influencing the line-widths, or T2 s, can be examined more directly by studying the influence of molecular weight. It is well established that the zero shear bulk viscosity of all amorphous polymers is directly proportional to the molecular weight below a critical low molecular weight, M., and above this molecular weight increases as the 3.5 power of M. ( ) ( ) (50) M, represents approximately... 

The influence of molecular weight, polymerisation process, monomer type and neutralisation have been studied. 

The presence of poly(vinylpyrrolidone) in the system increases substantially molecular weight of poly(L-leucine) obtained. If the ratio of template to monomer is 1.35, the molecular weight is more then 10 times higher than for the blank reaction. The influence of molecular weight of PVP template on the molecular weight of the daughter polymer was very significant as seen from the Table 6.4. 

Chapman, Pearce, and Avens (4, 20) investigated the relation between chemical composition and insecticidal efficiency of various dormant and foliage spray oils against several common insect pests of deciduous trees, and found it to be positive. They concluded that an oil which is highly paraffinic in character is the most desirable type. Saturated narrow-cut petroleum fractions were used by Pearce, Chapman, and Frear 21) in a study of the influence of molecular weight and structural constitution on the insecticidal efficiency of such oils to eggs of the oriental fruit moth, Grapholitha molesta (Busck). Correlations between efficiency and various properties were compared on the basis of composition. The value of paraffinicity was illustrated, and the importance of other properties was indicated. 

In particular, Table 2.1 shows for atactic polystyrenes (in ref. 68 also isotactic polystyrene has been investigated, yielding C = —10300 Br in bromoform) that the influence of molecular weight (measurements in bromo-benzene and on the bulk polymer) is negligible or rather small. 

Dschagarowa E, Mennig G (1977) Influence of molecular weight and molecular conformation of polymers on turbulent drag reduction Rheol Acta 16 309... 

Blumstein, R. B. and Stickles, E. Influence of molecular weight on some properties of polymeric liquid crystals. Proc. 28th Macromol. Symp. IUPAC, U. Mass., Amherst, MA, p. 799, 1982... 

Fig. 4 Influence of molecular weight Mw on (a) lamellar arrangement and (b) diffraction patterns of polyethylene (c) comparison of the diameter Dk of molecular coils and of the long period L of the lamellar structure (after Michler [12])...

Maitani, Y., Y. Machida, and T. Nagai. 1989. Influence of molecular weight and charge on nasal absorption of dextran and DEAE-dextran in rabbits. Int J Pharm 49 23. 

Niimi, A.J. and B.G. Oliver. 1987. Influence of molecular weight and molecular volume on the dietary absorption efficiency of chemicals by fish. Canadian Journal of Fisheries and Aquatic Sciences 45 222-227. 

Fig. 12. Influence of Molecular Weight and End Capping on TMA behavior of polyimide homopolymers (in air, 10 °C/min)...

Chae, S.Y., Jang, M.-K. and Nah, J.-W. (2005) Influence of molecular weight on oral absorption of water soluble chitosans. J. Control. Release 102 383-394. 

Bernkop-Schnurch A, Humenberger C, Yalenta C (1998) Basic studies on bioadhesive delivery systems for peptide and protein drugs. Int J Pharm 165(2) 217-225 Chae SY, Jang M-K, Nah J-W (2005) Influence of molecular weight on oral absorption of water soluble chitosans. J Control Rel 102(2) 383-394 Cho EC, Lim HJ, Shim J, Park JY, Dan N, Kim J, Chang I-S (2007) Effect of polymer characteristics on structure of polymer-liposome complexes. J Colloid Interf Sci 311(1) 243-252... 

The significant influence of molecular weight on viscosity becomes evident during processing if, for example, polymers degrade and the molar mass decreases, the viscosity and therefore the pressure build-up in the extruder can decrease sharply. 

Fox, T. G., and P. J. Flory Second-order transition temperatures and related properties of polystyrene. I. Influence of molecular weight. J. Appl. Phys. 21, 581 (1950). 

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