Sequence distribution of styrene-butadiene copolymer initiated by n-butyllithium

Tanaka, Yasuyuki; Sato, Hisaya; Nakafutami, Yasunobu; Kashiwazaki, Yasushi

doi:10.1021/ma00246a022

Cited by 15 publications

(7 citation statements)

References 1 publication

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“…In region II, M n,app or M n starts to rapidly increase again with time at 7.8 ≤ t / h ≤ 10, followed by a slow increase to a final value. The observed two-step increase in M n,app or M n with t is very consistent with the results previously reported for the simultaneous copolymerization. ,, As for M w / M n , at t = 0.5 h, the earliest accessible reaction time in this study, M w / M n is ∼1.054. As the polymerization reaction proceeds, it slightly decreases to a constant value of 1.045, as expected.…”

Section: Resultssupporting

confidence: 92%

Combined SANS, SEC, NMR, and UV−vis Studies of Simultaneous Living Anionic Copolymerization Process in a Concentrated Solution: Elucidation of Building-Up Processes of Molecules and Their Self-Assemblies

et al. 2010

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A simultaneous living anionic copolymerization of a concentrated solution of deuterated styrene (S) and nondeuterated isoprene (I) monomers in deuterated benzene as a solvent was studied by a combination of time-resolved measurements of small-angle neutron scattering (SANS), size exclusion chromatography (SEC), nuclear magnetic resonance (NMR), and ultraviolet−visible spectroscopy (UV−vis). The molecular building-up process and its consequence on the bottom-up self-assembling process during the copolymerization reaction were observed on three different length scales on the same batch of the solution, which enabled us to explore simultaneously the time changes in the local structure (living chain ends), the primary structure (propagating chains), and the higher order structure (microdomains). We found that the copolymerization process was divided into two time regions, defined by regions I and II. In region I, the copolymerization of S and I monomers took place, and all I monomers were consumed at the end of region I. In the early stage of region I (region Ia), the SANS profiles were almost time-independent and exhibited no scattering maximum, whereas in the late stage of region I (region Ib), a scattering maximum appeared at q m and hardly changed with time, although the maximum intensity I m slightly increased with time. In region II, pure polystyrene (PS) block chains were formed. q m and I m rapidly decreased and increased, respectively, and the polymerization-induced disorder−order transition (ODT) and order−order transition (OOT) were observed. The living polymers having isoprenyl anion at the chain end (denoted hereafter by PI) started to change into those having styryl anion at the chain end (denoted hereafter by PS), and hence the polymerization of S monomers occurred under the coexistence of PI− and PS−. As a consequence, we found an increase in the polydispersity index of the molecular weight, M w/M n, and a slower effective reaction rate of S monomers relative to the corresponding homopolymerization of S monomers.

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Section: Resultssupporting

confidence: 92%

Combined SANS, SEC, NMR, and UV−vis Studies of Simultaneous Living Anionic Copolymerization Process in a Concentrated Solution: Elucidation of Building-Up Processes of Molecules and Their Self-Assemblies

et al. 2010

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“…This is because the development of controlled radical polymerization4–6 in the 1990s has allowed for the relatively straightforward synthesis of gradient copolymers from addition‐type monomers using semibatch or, in some cases, batch reactions 7–27. In contrast, anionic polymerization, which has been used for many decades in synthesizing block copolymers from addition‐type monomers, is not generally well suited to the synthesis of gradient copolymers because of the very large differences in reactivity ratios typically observed in anionic copolymerizations 28–31. Thus, there is usually a very strong preference for the addition of one monomer, leading to a mostly blocky copolymer structure or tapered block copolymer when anionic polymerization is used in attempts to produce gradient copolymers 28–30.…”

Section: Introductionmentioning

confidence: 99%

“…In contrast, anionic polymerization, which has been used for many decades in synthesizing block copolymers from addition‐type monomers, is not generally well suited to the synthesis of gradient copolymers because of the very large differences in reactivity ratios typically observed in anionic copolymerizations 28–31. Thus, there is usually a very strong preference for the addition of one monomer, leading to a mostly blocky copolymer structure or tapered block copolymer when anionic polymerization is used in attempts to produce gradient copolymers 28–30. (Tapered block copolymers differ from gradient copolymers as they have a composition gradient over a minority of the copolymer chain length and are expected to exhibit behavior much more like that of block copolymers than gradient copolymers.)…”

Section: Introductionmentioning

confidence: 99%

Breadth of glass transition temperature in styrene/acrylic acid block, random, and gradient copolymers: Unusual sequence distribution effects

Wong

Kim

Torkelson

2007

J Polym Sci B Polym Phys

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Block, random, and gradient copolymers of styrene (S) and acrylic acid (AA) are synthesized by conventional or controlled radical polymerization, and their glass transition temperature (T g ) behaviors are compared. The location and breadth of the T g s are determined using derivatives of differential scanning calorimetry heating curves. Each S/AA random copolymer exhibits one narrow T g , consistent with a single phase of limited compositional nanoheterogeneity. Block copolymers exhibit two narrow T g s originating from nanophase separation into ordered domains with nearly pure S or nearly pure AA repeat units. Each gradient copolymer exhibits a T g response with a $50-56 8C breadth that extends beyond the upper T g of the block copolymers. For copolymers of similar composition, the maximum value in the gradient copolymer T g response is consistent with that of a random copolymer, which has an enhanced T g relative to poly(acrylic acid) due to more effective hydrogen bonding when AA units are separated along the chain backbone by S units. These results indicate that gradient copolymers with ordered nanostructures can be rationally designed, which exhibit broad glass transitions that extend to higher temperature than the T g s observed with block copolymers. V V C 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45:

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“…We have established a novel method for the analysis of the sequence distribution of styrene and styrene−1,2 units in styrene−butadiene copolymers (SBR) by the GPC analysis of ozonolysis products. − This ozonolysis−GPC method has proven to be a powerful tool for analysis of the entire sequence distribution from short to long sequences in commercial SBRs. , The method was applied to the analysis of the sequence distribution of 1,2 units in polybutadiene by GPC measurement of ozonolysis products, which were transformed into trifluoroacetates after reductive degradation of the ozonide with LiAlH 4 . A commercial polybutadiene showed GPC peaks corresponding to 1,4−1,4 and 1,4−(1,2) n −1,4 sequences from n = 1 to 9 using a refractive index (RI) detector.…”

Section: Introductionmentioning

confidence: 99%

Quantitative Analysis of Sequence Length Distribution of 1,2 Units in Polybutadienes by Ozonolysis−GPC Method

et al. 1999

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The sequence distribution of 1,2 units in commercial and laboratory produced polybutadienes, containing 1,2 units from 0.5 to 87%, was analyzed by an ozonolysis−GPC method. Ozonides from polybutadiene were converted to trifluoroacetates by reduction with LiAlH4, followed by esterification with trifluoroacetic anhydride. The trifluoroacetates derived from 1,4−1,4 and 1,4−(1,2) n −1,4 sequences, from n = 1 to 7, were observed as respective GPC peaks using an refractive index detector. The relative intensities of these peaks were converted to the concentration of each sequence by using correction factors determined with model compounds and by direct weighing of each peak. Polybutadienes prepared by anionic polymerization showed a sequence distribution of 1,2 and 1,4 units corresponding to Bernoulian statistics, whereas the 1,4−(1,2)2−1,4 sequence was significantly higher than the theoretical value for 1,2 units in cis-1,4 polybutadiene.

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Sequence distribution of styrene-butadiene copolymer initiated by n-butyllithium

Cited by 15 publications

References 1 publication

Combined SANS, SEC, NMR, and UV−vis Studies of Simultaneous Living Anionic Copolymerization Process in a Concentrated Solution: Elucidation of Building-Up Processes of Molecules and Their Self-Assemblies

Combined SANS, SEC, NMR, and UV−vis Studies of Simultaneous Living Anionic Copolymerization Process in a Concentrated Solution: Elucidation of Building-Up Processes of Molecules and Their Self-Assemblies

Breadth of glass transition temperature in styrene/acrylic acid block, random, and gradient copolymers: Unusual sequence distribution effects

Quantitative Analysis of Sequence Length Distribution of 1,2 Units in Polybutadienes by Ozonolysis−GPC Method

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