Star-branched

By water, SPreparation and Properties of Star-branched Polymers. Vol. 30, pp. 89—116. 

Spot tests, 245 Spray elastomers, 204 Star-branched polymers, 187 Star copolymers, 7... 

Investigation of the linear viscoelastic properties of SDIBS with branch MWs exceeding the critical entanglement MW of PIB (about -7000 g/mol ) revealed that both the viscosity and the length of the entanglement plateau scaled with B rather than with the length of the branches, a distinctively different behavior than that of star-branched PIBs. However, the magnitude of the plateau modulus and the temperature dependence of the terminal zone shift factors were found to... 

In a seminal and seemingly forgotten paper, Burchard et al. " discussed the analysis of various polymer architectures based on integrated light scattering (LS) and quasielastic light scattering (QELS). They considered mono- and polydisperse linear and star-branched polymers with/number of arms ( rays ), and random polycondensates of Af or ABC type (identical or different... 

Puskas, J.E., Pattern, W.E., Wetmore, P.M., and Krukonis, A. Multiarm-star polyisobutylene-polystyrene thermoplastic elastomers from a novel multifunctional initiator, Polym. Mater. Set Eng., 82,42 3, 1999. Brister, L.B., Puskas, J.E., and Tzaras, E. Star-branched PIB/poly(p-t-bu-Styrene) block copolymers from a novel epoxide initiator, Polym. Prepr., 40, 141-142, 1999. 

Isobutylene-based elastomers include HR, the copolymer of isobutylene and isoprene, halogenated HR, star-branched versions of these polymers, and the terpolymer isobutylene-p-methylene styrene-bromo-p-methyl styrene (BIMS). A number of recent reviews on isobutylene-based elastomers are available [33-35]. 

Hancock, D. O. and Synovec, R. E., Rapid characterization of linear and star-branched polymers by concentration gradient detection, Anal. Chem., 60,2812, 1988. 

Star-branched butyl rubber, 4 437-438 copolymers, 4 445-446 Starch(es), 4 703-704, 20 452-453 as blood substitute, 4 111-112 cationic, 18 114-115 in cereal grains, 26 271-274 in cocoa shell from roasted beans, 6 357t compression effects in centrifuges, 5 513 depolymerization, 4 712 in ethanol fermentation, 10 534—535 etherified, 20 563 as a flocculant, 11 627 high-amylose, 26 288 Mark-Houwink parameters for, 20 558t modified and unmodified, 12 52-53 in paper manufacture, 18 122-123 performance criteria in cosmetic use, 7 860t... 

B11 < B < l>1. Now, in addition to pure HS, there is a new branch of compact stars, the hybrid stars but the nucleation time r(MHs,max) to form a droplet of Q -matter in the maximum mass hadronic star, is of the same order or much larger than the age of the Universe. Therefore, it is extremely unlikely to populate the hybrid star branch. Once again, the compact star we can observe are, in this case, pure HS. 

BIU < B < l>11. In this case, the critical mass for the pure hadronic star sequence is less than the maximum mass for the same stellar sequence, i.e., Mcr < Mus,max- Nevertheless (for the present EOS model), the baryonic mass Mb(Mcr) of the hadronic star with the critical mass is larger than the maximum baryonic mass MqS max of the hybrid star sequence. In this case, the formation of a critical size droplet of deconfined matter in the core of the hadronic star with the critical mass, will trigger off a stellar conversion process which will produce, at the end, a black hole (see cases marked as BH in Tab. 1 and Tab. 2). As in the previous case, it is extremely unlikely to populate the hybrid star branch. The compact star predicted by these EOS models are pure HS. Hadronic stars with a gravitational mass in the range Mhs(MqS rnax) < Mhs < Mcr (where MqS max is the baryonic mass of the maximum mass configuration for the hybrid star sequence) are metastable with respect to a conversion to a black hole. 

Postpolymerization of difunctional monomers to effect star branching has been successfully applied in cationic polymerization, e.g. in the case of polyisobutylene initiated with 2-chloro-2,4,4,-trimethylpentane/TiCl4. Addition of divinylbenzene leads to star polymers [104], Vinyl ethers, when polymerized with HI/ZnI2 in toluene at — 40°C, can be copolymerized with divinylether... 

DIVERGENT SYNTHESIS OF PAMAM DENDRIMERS VIA EXCESS REAGENT METHOD PREPARATION OF ESTER TERMINATED PAMAM STAR-BRANCHED PRECURSOR [NH2-(CH2)2 6-NH21 (G = -0.5) STAR-PAMAMICO E) [1]... 

PREPARATION OF AMINE TERMINATED PAMAM STAR-BRANCHED PRECURSOR [NH2-(CH2)2 6-NHJ ... 

Application to Randomly End Linked Star-Branched Polystyrenes. 169... 

As already outlined, star branched macromolecules resemble their linear chain analogues. The behavior becomes evident when for a given number of arms f the... 

Schaefgen and Flory [79] were the first to observe this effect. They prepared star-branched polyamides by co-condensation of A-B types of monomers with central units which carried/-functional A groups. By this technique star molecules were obtained in which the arms are not monodisperse in length. They rather obeyed the Schulz-Flory most probable length distribution with polydis-persity index However, the coupling of f arms onto a star center leads... 

Fig. 9. Molar mass dependencies of the intrinsic viscosity of star-branched polyamides obtained by co-condensation of bifunctional amino acids with f-functional polyacids. The curves appear shifted towards smaller intrinsic viscosities as the functionality of the star center was increased [79]. Reprinted with permission from [79]. Copyright [1948] American Society...

Fig. 13. Chain length dependence of the second virial coefficient A2 for some star branched macromolecule, according to Casassa (full line). The data points correspond to measurements [89] (triangles 3-arm, circles 12-arm and rhombus 18-arm stars. Reprinted with permission from [89]. Copyright [1984] American Society...

The Schulz-Zimm distribution would be found for/end-to-end coupled linear chains which obey the most probable distribution, as well as for/of such chains which are coupled onto a star center. This behavior demonstrates once more the quasi-linear behavior of star branched macromolecules. In fact, to be sure of branching, other structural quantities have to be measured in addition to the molar mass distribution. 

In contrast to star-branched macromolecules, this relationship differs now from that of the non-fractionated samples... 

Fig. 22. KMHS relationships for the fractions of end-linked 3-arm star-branched polystyrene molecules and of linear polystyrene fractions. The data refer to three samples of different in the pregel state and one from the sol fraction of a gel. The curves for the branched macromolecules coincide within experimental error in the high molar mass region. The deviations at lowM result from a different amount of non-reacted end-functionalized stars. The exponents of the end-linked and linear PS chains are a =0.42 0.02 while that of linear chains is 0.70 0.01 [95,120,123,124]. Reprinted with permission from [95]. Copyright [1997] American Society...

Fig. 24. Contraction factors for star-branched macromolecules as a function of the number of arms. The full line represents strictly regular stars, the dashed line one that for stars with polydisperse arms (MyM =2), the dotted line according to Daoud and Cotton [29]. The symbols represent the data from the literature. The deviation at large / represents the stretching of the arms due to overcrowding...

Thus a simple power law behavior with an exponent of 1.5 would result if 0"= 1 [125]. Zimm and Kilb [128] made a first attempt to calculate g for star branched macromolecules on the basis of the Kirkwood-Riseman approximation for the hydrodynamic interaction. They came to the conclusion that... 

Fig. 25. The viscosity contraction factor g as a function of the geometric contraction factor g for star-branched macromolecules ( 3-128). No distinction was made between the chemical nature of the various arms and between the thermodynamic quality of the solvents used. See Table 3...

---