Shape polymers

Average moleeular weight development can be measured directly through GPC or SEC, as we mentioned earlier. These measurements have their own problems, but can be very useful when properly tested and interpreted. They provide an excellent basis for predicting PF performance. They can also give an overview of PF eondensation kinetics and even some information about polymer shapes. However, they do not provide detailed information on the chemical structure of the polymer. Such information is required to propose reasonable mechanisms. C-... 

The use of computers as an additional tool in studying polymer shapes is discussed. A general discussion of molecular modeling is presented with specific application to polymers. An example relating hydrodynamic properties of hyaluronic acid to computer generated models is included. 

The supramolecular transformation from sphere to cylinder is supported by X-ray data indicating that the spherical polymers adopt a cubic phase, whereas the cylindrical polymers adopt a hexagonal phase [23b]. Further studies involving a library of dendritic macromonomers led to the conclusion that the effect of DP on polymer shape is a general phenomenon [24], More recently, scanning... 

The second approach uses multiple detectors (Figure 3.13), allowing a double extrapolation to zero concentration and zero angle with the data forming what is called a Zimm plot (Figure 3.14). The extrapolation to zero angle corrects for finite particle size effects. The radius of gyration, related to polymer shape and size, can also be determined from this plot. The second extrapolation to zero concentration corrects for concentration factors. The intercepts of both plots are equal to /M . 

The FALLS or MALLS detector measures r-related values a differential refractive index (DRI) detector is used to measure concentration, and the SEC supplies samples containing fractionated polymer solutions allowing both molecular weight and MWD to be determined. Further, polymer shape can be determined. This combination represents the most powerful one, based on ease of operation, variety of samples readily used, cost, means to determine polymer size, shape, and MWD available today. 

We are continuing to recognize that polymer shape is important in determining material property. Another group of structurally complex shapes is referred to as stars. There are a... 

While the specific chemistry and physics dealing with synthetic polymers is complicated, the chemistry and physics of natural polymers is even more complex because of a number of related factors, including (1) the fact that many natural polymers are composed of different, often similar but not identical, repeat units (2) a greater dependency on the exact natural polymer environment (3) the question of real structure of many natural polymers in their natural environment is still not well known for many natural polymers and (4) the fact that polymer shape and size are even more important and complex in natural polymers than in synthetic polymers. 

The size and shape of polymers are intimately connected to their properties. The shape of polymers is also intimately connected to the size of the various units that comprise the macromolecule and the various primary and secondary bonding forces that are present within the chain and between chains. This chapter covers the basic components that influence polymer shape or morphology. 

Percec V, Ahn CH, Ungar G, Yeardley DJP, MoUer M, Sheiko SS. ControUing polymer shape through the self-assembly of dendritic side-groups. Natrrre (Loud) 1998 391 161-164. 

V. Percec, C.H. Ahn, G. Ungar, D.J.P. Yeardley, M. Moller, S.S. Sheiko, Controlling Polymer Shape through the Self-Assembly of Dendritic Side-Groups , Nature, 391, 161 (1998)... 

It should be noted that as polymer size in solution is related to not only molecular weight, but also polymer shape or conformation, polymer standards of the same homologous series should be used for calibration if a true molecular weight distribution is required. 

These two descriptors can be combined to produce an effective polymer shape parameter, called order parameter g, such as ... 

The photoinduced deformation phenomenon of materials is called a photomechanical effect, and it has been so far reported for photoresponsive polymer films and gels [35-43]. When azobenzene is isomerized from the trans form to the cis form, the length of the molecule is shortened from 0.90 to 0.55 nm. The size change of the molecule on photoirradiation is expected to alter the shape of the polymers which contain the azobenzene molecules. However, it is not the case in polymer systems. The transformation in polymer films does not change the polymer shape because of the large free volumes of the polymer bulk. Suitable organization or assembly of the molecules is required for the photoinduced deformation of materials. 

Polymer properties are directly dependent on both the Inherent shape of the polymer and on its treatment. Contributions of polymer shape to polymer properties are often complex and interrelated, but can be broadly divided into terms dealing with chain flexibility, chain regularity, interchain forces, and steric effects. 

In dilute solutions, demixtion is preceded by change of the polymer shape which becomes more compact this is the coil-globule transition. Consequently, though both effects are related, two different types of studies appeared. 

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