Regular star polymers

Different types of LCB are distinguished. Star polymers are the simplest branched polymers because they have only one branch point. Regular star polymers have a branch point with a constant number (functionality,/) of arms and every arm has the same molecular weight. They are therefore monodisperse polymers. Star polymers may also have arms with a most probable distribution [5], Star polymers can also be polydisperse due to a variable functionality. Palm tree [6] or umbrella polymers [7] that contain a single arm with different molecular weight (MW) than the other arms are classified under the asymmetric star [8] polymers, see Figure 3.2. 

Figure 3.2 Regular star polymers with f= 3 and f=6 and an asymmetric palm tree or umbrella polymer.

Since the successful synthesis of dendritic macromolecules from low MW monomers [14a], research has also been performed in the area of dendritic polymers [14b, 15]. Dendritic polymers are obtained by attaching or growing several end-standing arms onto a central regular star polymer. This procedure is repeated in a generational manner, see Figure 3.3. 

Schematically, model regular star polymers are obtained directly from living anionic polymers where (Si-Cl p is a multifunctional carbosilane coupling agent, MeSiCl3, SiCl4, Cl3SiCH2CH2SiCl3, etc. including dendritic carbosilanes...

The effect of the quality of the solvent on the dimensions of dendrimers has been considered [54]. The size of the dendrimers increases with an increased interaction with solvent. However, in contrast to linear polymers or regular star polymers, the exponent v in Eq. (4) was found to be independent of the quality of the solvent for high MW dendrimers [54]. 

Roovers, J. Dilute solution properties of regular star polymers. Plast. Eng. 1999, 53, 285-341. 

Nonlinear polymers primarily include star, miktoarm star, and H-type (co)polymers, hyperbranched dendrimers, and dendrimer-like star polymers. Homo-arm (or regular) star polymers contain multiple arms of identical chemical composition and similar molecular weight connecting to a central... 

The best fit to data on branched polymers can be made by choice of values of (1/3-X2)- Figure 6 shows such a fit to (1/3—X2) = 0.045 for a series of four and six-branched regular star polymers. Semi-quantitative agreement is achieved although the 0 depression disappears m< e rspidly as molecular weight is increased than is predicted. The effect of solvent on deviations of 0. 2 has been investigated for... 

Roovers, J. (1999) Dilute solution properties of regular star polymers, in Star and Hyperbnmched Polymers (eds. M.K. Mishra, and S. Kobayashi), Marcel Dekker Inc., New York, pp. 285 341. 

Several possibilities are to be considered here If these second-generation branches are much longer than the first generation arms, the species obtained can be considered to be a regular star polymer. The effective core, to which the long second-generation branches are attached, includes the short first-generation branches. In principle, provided no deactivation occurs, the number of... 

Dilute Solution Properties of Regular Star Polymers... 

The regular star polymer has the simplest branching architecture because the star architecture can be characterized by a single parameter/ the function-... 

Fortunately, powerful experimental methods are available to prepare regular star polymers with full control over their arm molecular weight and functionality. The properties of regular star polymers have been reviewed [3,4]. Other reviews, in the context of branched polymers, are also available [5-7]. Specialized topics on branched polymers in comparison with linear polymers have also been covered [8-12]. 

This review deals with the static and dynamic properties of regular star polymers at zero concentration and with the dependence of these properties on the polymer concentration in dilute solution. We stress the experimental results and make comparisons with theoretical models and computer simulations. 

Because of the fundamental nature of the size of polymer coils, considerable effort has been devoted to the experimental measurement of the size of regular star polymers both in good solvents and under 6-conditions. The size of a polymer coil is obtained from the angular dependence of scattered radiation at low angles. The angular dependence of the intensity of light (or neutrons) scattered by a polymer solution is analyzed in terms of the product of the form factor, P Q), and the structure factor, S Q) ... 

TTie form factor of a regular star polymer has been derived under the assumption of the Gaussian segment distribution [22,23] ... 

Figure 7 Schematic two-dimensional representation of the blob model of a regular star polymer in dilute solution.

In this section the dependence of the second virial coefficient on the functionality of regular star polymers in good solvent is considered. Typical results of the second virial coefficient as a function of molecular weight are shown in Figure 12 for different star fimctionalities. It can be seen that A2 of stars with... 

Values of obtained on linear pol)miers and on regular star polymers have been collected in Table 12. The polystyrene results are based on sedimentation experiments. The polybutadiene results are from dynamic light scat-... 

The book also covers the solution properties of the regular star polymers. This class of materials has been known for many years to polymer chemists however, rapid development has occurred only ce tiie proposal of the idea of dendritic polymers in the mid-1980s. The characteristics of tiie polymers discussed here include the size and shape of the molecules, their biological activities, their low viscosity in solution, their substrate-holding properties inside the molecule, etc. The unique properties of these polymers attract many chemists, not only in polymer chemistiy but also in organic chemistry, biochemistry, medicine, oiganometaUic chemistry, catalyst chemistry, and so on, for these new materials are e q)ected to find applications in many... 

Among many types of branched polymers, star polymers have the simplest stmeture with only one branching point in each molecule. The chains connected to the branching point are usually called the arms. If we use the living polymerization technique, we can obtain regular star polymers having a fixed number of arms with equal length. ... 

Solution properties of regular star polymers were intensively studied by Roovers et and Fetters et... 

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