Poly star shape

More recent examples include end-functionalized multiarmed poly(vinyl ether) (44), MVE/styrene block copolymers (45), and star-shaped polymers (46—48). With this remarkable control over polymer architecture, the growth of future commercial appHcations seems entirely likely. 

Platinum-cobalt alloy, enthalpy of formation, 144 Polarizability, of carbon, 75 of hydrogen molecule, 65, 75 and ionization potential data, 70 Polyamide, 181 Poly butadiene, 170, 181 Polydispersed systems, 183 Polyfunctional polymer, 178 Polymerization, of butadiene, 163 of solid acetaldehyde, 163 of vinyl monomers, 154 Polymers, star-shaped, 183 Polymethyl methacrylate, 180 Polystyrene, 172 Polystyril carbanions, 154 Potential barriers of internal rotation, 368, 374... 

A change of architecture is another route that enables diversification of the properties of aliphatic polyesters. This review will focus on star-shaped, graft, macrocyclic, and crosslinked aliphatic polyesters. It must be noted that the ROP of lactones has been combined with several other polymerization mechanisms such as ROP of other heterocyclic monomers, ionic polymerization, ROMP, and radical polymerization. Nevertheless, this review will not cover these examples and will focus on polymers exclusively made up of poly(lactone)s. 

Turunen MPK, Korhonen H, Tuominen J, Seppala JV (2001) Synthesis, characterization and crosslinking of functional star-shaped poly(E-caprolactone). Polym Int 51 92-100... 

Elkins C, Viswanathan K, Long TE. Synthesis and characterization of star-shaped poly(ethylene-co-propylene) polymers bearing terminal self-complementary multiple hydrogen-bonding sites. Macromolecules 2006 39 3132-3139. 

Karikari A, Mather BD, Long TE. Association of star-shaped poly(D,L-lactide)s containing nucleobase multiple hydrogen bonding. Biomacromolecules 2007 8 302-308. 

Mather BD, Elkins CL, Beyer FL, Long TE. Morphological analysis of telechelic ureidopyr-imidone functional hydrogen bonding linear and star-shaped poly(ethylene-co-propylene)s. Macromol Rapid Commun 2007 28 1601-1606. 

Riess demonstrated recently that poly(styrene-b-oxirane) copolymers could act as non-ionic surfactants and lead to water/ toluene microemulsions (29, 30). Using isopropanol as cosurfactant, both 0/W and W/0 microemulsions are obtained (3l). This is a very important conclusion, since PO based diblock copolymers give rise only to 0/W microemulsions under the same experimental conditions (8, 31,). In this respect the "branched structure" of the PO hydrophilic component could favor a decrease in the packing density of the inverse micelle forming molecular and explain the different behavior of the linear and star-shaped PS/PO block copolymers in the W/0 microemulsification process. 

Worsfold found that the degree of association as measured from viscosity was less than that indicated by the light scattering and spectroscopic results. It was therefore concluded that the association dissociation rates were comparable to the chain entanglement lifetime. As a consequence, Worsfold concluded that viscosity measurements involving concentrated solutions of poly(dienyl)lithium in the entanglement regime could not detect the presence of, for example, star-shaped tetramers if the equilibrium... 

It should also be noted that the viscometric technique can detect the presence of star-shaped aggregates, having the ionic active centers. The addition of ethylene oxide to hydrocarbon solutions of poly(isoprenyl)lithium leads to a nearly two-fold increase in viscosity144). Conversely, this results in an approximately twenty-fold decrease in solution viscosity, after termination by the addition of trimethylchloro-silane. This change in solution viscosity is reflected in the gelation which occurs when difunctional chains are converted to the ionic alkoxy active centers 140,145,146). Branched structures have also been detected 147> by viscometry for the thiolate-lithium active center of polypropylene sulfide) in tetrahydrofuran. 

Some new star-shaped poly(l,5-dioxapan-2-one) polymers have been prepared by ROP (Equation 23) <2002PSA2049>. 

Aliphatic star-shaped polyesters of l-LA have been synthesized [114, 115] with multifunctional hydroxy compounds as initiators. The crystallinity of the star-shaped poly(L-LA) was found to be higher than that of the corresponding linear counterpart. Star-shaped poly(L-LA) has also been block copolymerized with trimethylene carbonate/e-CL [116] This resulted in a less brittle and considerably toughened material. 

Copolymerization of TMC with e-CL or L-lactide has been reported to be useful for modifications of the polymer properties [144,218,280,283]. The molecular architecture presents a powerful tool for obtaining new materials with interesting properties. For instance, a star-shaped rubbery poly(TMC-co-CL) was synthesized. d,L-LA/GA polymerization was then initiated from the hydroxy terminated arms to yield a poly(TMC-co-CL)-block-PLGA [284]. 

Osaki K, Mitsuda G, Johnson R, Schrag J, Ferry JD (1972a) Infinite-dilution viscoelastic properties of linear and star-shaped polybutadiene. Macromolecules 5(1) 17-19 Osaki K, Schrag J, Ferry JD (1972b) Infinite-dilution viscoelastic properties of poly (a-methylstyrene). Applications of Zimm theory with exact eigenvalues. Macromolecules 5(2) 144-147... 

Fig. 1A-E. MWD of the products obtained from the reaction of living poly(IBVE) with divinyl ether 1 in toluene at - 40 °C DParm=38, [living ends]=8.3 mmol l"1, r=5.0 A living po-ly(IBVE) [IBVE]0=0.38 mol l"1, [HI]0=10 mmol l-1, [Znl2]0=0.2 mmol l"1, IBVE conversion 00% in 45 min B-E the products recovered after the reaction with 1. Reaction time after addition of 1 (B) 10 min, (C) 30 min, (D) 1 h, (E) 18 h [star-shaped poly(IBVE)]. Reprinted with permission from [3]. Copyright 1991 Am. Chem. Soc.

The g factors of some star-shaped polymacromonomers with relatively limited number of arms have been investigated and compared with the theory mentioned above. Tsukahara et al. [61] estimated the g factors of PSt polymacromonomers from 24 by SEC-LALLS measurement and compared with Eqs. (6) and (8). The results suggest that these poly(macromonomers) behave like star polymer. The experimental value of g is larger than the theoretical one based on Eq. (6) in agreement with results of studies on model star polymers [62]. 

Star-shape Poly(vinylmethyl-co-dimethyl)siloxanes with Carbosilane Core - Synthesis and Application... 

We would like to report the synthesis of a star-shape poly(vinylmethyl-c6>-dimethyl)siloxane polymers functionalized in their exterior, which makes them especially suitable for application as catalytic supports. Similarly to catalysts bound to periphery-functionalized dendrimers [3] they offer regularly distributed and available catalytic sites. 

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