Synthesis of high molecular weight ring polystyrenes

Roovers, Jacques; Toporowski, P. M.

doi:10.1021/ma00240a002

Cited by 363 publications

(357 citation statements)

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“…g′ values between 0.73 and 0.75 were obtained. This ratio is higher than the values of 0.66-0.68 found by Roovers et al 2 and Leppoittevin et al 7 However, an expansion to the dimensions of a cyclic copolymer is expected since an increased number of heterocontacts is expected to be present between incompatible polymeric blocks. Iatrou et al 35 found a similar influence of the heterocontacts on the dimensions of 3-miktoarm stars of the A 2 B type in dilute solution.…”

Section: Resultsmentioning

confidence: 58%

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Synthesis and Characterization of Model Cyclic Block Copolymers of Styrene and Butadiene. Comparison of the Aggregation Phenomena in Selective Solvents with Linear Diblock and Triblock Analogues

Iatrou¹,

Hadjichristidis²,

Meier³

et al. 2002

Macromolecules

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The synthesis and characterization of model cyclic diblock copolymers of styrene (St) or perdeuterated styrene (St-d8) and butadiene (Bd) are presented. Since conventional methods of characterization cannot separate completely the cyclic copolymer from its linear precursor, differences in the micellar behavior were used as a method for investigation of their purity. For this purpose, in addition to the cyclic and linear triblock copolymers, two linear diblocks with similar compositions, and molecular weight equal or half of the cyclic diblocks, were also synthesized. The synthetic approach of the cyclics involved the reaction of (1,3-phenylene)bis(3-methyl-1-phenylpentylidene)dilithium initiator with butadiene in the presence of sec-BuOLi, followed by polymerization of . The cyclization of the resulting R,ω-difunctional triblock copolymer was performed by using bis(dimethylchlorosilyl)-ethane, under high dilution conditions. The copolymers were characterized by size exclusion chromatography, membrane osmometry, NMR and UV spectrometry, and viscometry. The micelles formed in the selective solvents n-decane (for PBd) and dimethylformamide (for PS-d 8) were characterized by smallangle neutron scattering and dynamic light scattering. It was found that the aggregation number of the cyclic copolymers was the smallest among the different macromolecular architectures. Moreover, the SANS data for the triblocks in n-decane indicated the presence of 37% dangling chains which did not appear in the data for the corresponding cyclic copolymers. Considering that 5% of dangling chains is possible to be detected, it proves that the cyclic copolymers are at least 87% pure. A scaling model was used in order to justify the difference in the aggregation numbers between the four different copolymers.

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Section: Resultsmentioning

confidence: 58%

“…[2][3][4][5][6][7][8][9][10] Due to the absence of free chain ends, the monomeric units of cyclic homopolymers are equivalent. Moreover due to the cyclic form of the molecules, the intramolecular interactions are increased, compared to a linear analogue.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Characterization of Model Cyclic Block Copolymers of Styrene and Butadiene. Comparison of the Aggregation Phenomena in Selective Solvents with Linear Diblock and Triblock Analogues

Iatrou¹,

Hadjichristidis²,

Meier³

et al. 2002

Macromolecules

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“…Corresponding author e-mail: kremer@mpip-mainz.mpg.de that this system presents a formidable challenge to the current polymer theories. It is of considerable current experimental interest [14][15][16][17][18][19][20] , and it is believed to have a significant projection on the problem of chromatin structure and dynamics in chromosomes. We refer the reader to the detailed discussion of these issues in the Introduction section of our paper 1 ; the large bibliography of relevant references is also in that paper.…”

Section: Introductionmentioning

confidence: 99%

Molecular dynamics simulation study of nonconcatenated ring polymers in a melt. II. Dynamics

Halverson¹,

Lee²,

Grest³

et al. 2011

The Journal of Chemical Physics

254

479

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Molecular dynamics simulations were conducted to investigate the dynamic properties of melts of nonconcatenated ring polymers and compared to melts of linear polymers. The longest rings were composed of N = 1600 monomers per chain which corresponds to roughly 57 entanglement lengths for comparable linear polymers. The ring melts were found to diffuse faster than their linear counterparts, with both architectures approximately obeying a D ∼ N −2.4 scaling law for large N . The mean-square displacement of the center-of-mass of the rings follows a sub-diffusive behavior for times and distances beyond the ring extension R 2 g , neither compatible with the Rouse nor the reptation model. The rings relax stress much faster than linear polymers and the zero-shear viscosity was found to vary as η 0 ∼ N 1.4±0.2 which is much weaker than the N 3.4 behavior of linear chains, not matching any commonly known model for polymer dynamics when compared to the observed mean-square displacements. These findings are discussed in view of the conformational properties of the rings presented in the preceding paper 1 .

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“…Ring polymers have been extensively studied experimentally by several groups, not always leading to completely consistent results [1][2][3][4][5]7,8]. Indeed, the synthesis of the samples of unknotted and nonconcatenated rings (see fig.…”

Section: Introductionmentioning

confidence: 99%

Topological effects in ring polymers: A computer simulation study

1996

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Unconcatenated, unknotted polymer rings in the melt are subject to strong interactions with neighboring chains due to the presence of topological constraints. We study this by computer simulation using the bond-fluctuation algorithm for chains with up to N = 512 statistical segments at a volume fraction Φ = 0.5 and show that rings in the melt are more compact than gaussian chains. A careful finite size analysis of the average ring size R ∝ N ν yields an exponent ν ≈ 0.39 ± 0.03 in agreement with a Flory-like argument for the topological interactions. We show (using the same algorithm) that the dynamics of molten rings is similar to that of linear chains of the same mass, confirming recent experimental findings. The diffusion constant varies effectively as D N ∝ N −1.22(3) and is slightly higher than that of corresponding linear chains. For the ring sizes considered (up to 256 statistical segments) we find only one characteristic time scale τ ee ∝ N 2.0(2) ; this is shown by the collapse of several mean-square displacements and correlation functions onto corresponding master curves. Because of the shrunken state of the chain, this scaling is not compatible with simple Rouse motion. It applies for all sizes of ring studied and no sign of a crossover to any entangled regime is found.

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Synthesis of high molecular weight ring polystyrenes

Abstract: collected by filtration without cooling and washed with hot toluene twice. The product, having the composition of 9,10-bis(diphenylphosphino)phenanthrene monosulfide, was obtained in a

Cited by 363 publications

References 5 publications

Synthesis and Characterization of Model Cyclic Block Copolymers of Styrene and Butadiene. Comparison of the Aggregation Phenomena in Selective Solvents with Linear Diblock and Triblock Analogues

Synthesis and Characterization of Model Cyclic Block Copolymers of Styrene and Butadiene. Comparison of the Aggregation Phenomena in Selective Solvents with Linear Diblock and Triblock Analogues

Molecular dynamics simulation study of nonconcatenated ring polymers in a melt. II. Dynamics

Topological effects in ring polymers: A computer simulation study

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