Star polystyrene

SBS (linear or star) Polystyrene Polybutadiene Polystyrene Polyethylene Thermoplastic elastomer... 

Figure 3.4 Intrinsic viscosity-molecularweight relation in toluene at 35°Cfor O regular H-polystyrene 12-arm star polystyrene A comb polystyrene with f= 30, Afbb = 2.75x 105 and increasing branch MW. Top line linear polystyrene...

Multifunctional initiators are found to be more effective in carbocationic than in carbanionic polymerization, because of the enhanced solubility of the less polar dormant initiating complexes. For example, the formation of a six-arm star polystyrene starts from... 

Hawker was the first to use a multifunctional TEMPO (2,2,6,6-tetramethyl-pyperidinyloxy-) initiator for the synthesis of a three-arm star polystyrene by the living free radical mechanism [114],... 

He also prepared a poly(styrene-g-styrene) polymer by this technique [114], The lack of crosslinking in these systems is indeed proof of the control achieved with this technique. An eight-arm star polystyrene has also been prepared starting from a calixarene derivative under ATRP conditions [115]. On the other hand, Sawamoto and his coworkers used multifunctional chloroacetate initiator sites and mediation with Ru2+ complexes for the living free-radical polymerization of star poly(methylmethacrylate) [116,117]. More recent work by Hedrick et al. [84] has demonstrated major progress in the use of dendritic initiators [98] in combination with ATRP and other methodologies to produce a variety of structure controlled, starlike poly(methylmethacrylate). 

Compounds containing two or more carbon-carbon double bonds also act as coupling agents and also as multifunctional initiators [Hadjichristidis et al., 2001 Quirk et al., 2000]. Such compounds can also be used to synthesize multifunctional initiators that subsequently produce star polymers. Consider l,3,5-tris(l-phenylethenyl)benzene (XL). Reaction with r-butyllithium produces a trifunctional initiator XLI, which initiates polymerization of a monomer such as styrene to form a 3-arm star polystyrene [Quirk and Tsai, 1998]. The 3-arm... 

Wyman and co-workers (120) studied the viscosity of narrow MWD linear and 4-armed star polystyrenes as a function of shear rate. At low shear rates, the star polymers (of MW 204000 and 430000) had low-shear viscosities much lower than linear ones of the same MW it may be remarked that the branch length... 

Six arm star polystyrenes were prepared by the core-first method using initiator 13 with six phenylethylchloride-type functions emanating from a central hexa-substituted benzene ring [24]. 

W.W. Graessley, J. Roovers Melt rheology of four-arm and six-arm star polystyrenes, Marcomol. 12 5 (1979) 959-965... 

Diffusional behaviour of star polystyrenes with different... 

Roovers J, By water S (1972) Preparation and characterization of four-branched star polystyrene. 5 384-388... 

Roovers J, Hadjichristidis N, Fetters LJ (1983) Analysis and dilute solution properties of 12- and 18-arm-star polystyrenes. Macromolecules 16 214-220... 

TABLE 1. Physical properties of star polystyrenes prepared by the incremental addition of divinylbenzene to a polystyrene anion having a of ronghly 26,000 daltons. 

Entry Increments of 0.74 ml of Divinyl Benzene Star Polystyrene Mn X 10" (daltons) Linking Efficiency (%) PDl Number of Arms... 

Exponential dependence of ij0 on Ma, as discussed earlier for star polymers, was also seen in the H-polymers. The crossover where rj0 of polystyrene H-polymers surpasses that of its linear homologues occurs at Mw 600000g/mol. This value is significantly lower than that observed for four-arm star polystyrenes [35]. Furthermore, the average entanglement of each of the five subchains of the H-polymers at this crossover is Ma 7Me, a value far lower than the level of arm entanglement required to reach the crossover in polystyrene star polymers. 

Polystyiene-polybutadiene Polybutadiene-poly(a-methyl styrene) Polybutadiene-poly(vinyl naphthalene) Polystyrene-polybutadlene-polystyrene Polybutadiene-polystyrene-polybutadiene Polystyrene-polyisoprene Pblystyrene-polyisoprene-polystyrene Polyia>prene-poly(vinyl-2-p dine) PofyiK>prene-poly(vinyl-4-pyridine) Polyisoprene-poly(methyl methacrylate) Polystyrene-poly(butadiene or ia>prene)-polystyrene Star polystyrene-polybutadiene with 4 branches Star polybutadiene-polystyrene with n branches Star polystyrene-polybutadiene with n branches Star polystyrene-polyisoprene with n brandies Polystyrene-polyisoprene-poly(vinyl-2-pyridine) Polystyrene-poly vinyl-2-pyridine) Polystyrene-poly(vinyl-4-pyridine) Poly(vinyl-2-pyridine)-poly(vinyl-4-pyridine)... 

An acetal-protected lithium initiator was used to polymerize styrene followed by linking with 1,3,5-triallyloxy-2,4,6-triazine to produce three-arm star polystyrenes.73 The protective acetal group was cleaved by weak acidic treatment in THF to give star polymers with terminal OH groups. These functional groups were coupled with toluene-2,4-diisocyanate to give randomly cross-linked products. Unfortunately, few characterization data were provided in this study. 

Other measurements reported (103) are for a symmetrical star polystyrene of nine arms. The polymer was synthesized by Zilliox et al. (65,107) by the addition of a small amount of divinyl benzene to a... 

The first experimental verification of these models came in 2000 when Foster et al. synthesized a six-arm star polystyrene using anionic polymerization... 

In 2008, Qian et al. synthesized two series of four-arm and eleven-arm star polystyrene with six different molar masses for each case. They determined surface tension of single component polymer film using a Wilhelmy plate technique... 

In the first case, the arms are grown from a single core with a given number of potentially active sites or a well-defined multifunctional initiator. In contrast to anionic multifunctional initiators, weU-defined soluble multifunctional cationic initiators are readily available. These multifunctional initiators with 3-8 initiating sites have been successfully applied for the synthesis of 3-8 arm star homo- and block copolymers of vinyl ethers, styrene and styrene derivatives, and IB. For example, six-arm star polystyrenes were prepared using initiator with six phenylethylchloride-type functions emanating from a central hexa-substituted benzene ring [250]. By subsequent end functionalization, a variety of end-functionaUzed A or (AB) (see above) star-shaped structures can also be obtained. 

Figure 26. Data of Kim, et aJ. [108], and fits to stretched exponentials, for (a) D of 900 kDa polystyrene in toluene, and (b) Dp of (top to bottom) methyl red, and 10, 35, 100, 390, 900, and 1800 kDa Dg polystyrenes through high-molecular-weight M/P > 3) polystyrene toluene matrix solutions. The left axis shows zero-matrix-concentration data, (c) Dp of polystyrenes [from top to bottom 379 kDa / = 3 star, 422 kDa linear chain, 1050 kDa linear chain, and 1190 kDa / = 3 star] through 1300 kDa polyvinyl-methylether orthofluorotoluene [110], and fits to linear (solid lines) and 3-armed star (dashed lines) data to eq. 16. (d) Dp of [111] 12-arm star polystyrenes (from top to bottom, of 55, 467, 1110, and 1690 kDa)in 140 kDa polyvinylmethylether ortho-fluorotoluene and fits to eq. 16.

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