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

Kakuta, Keiko; Tamai, Hironori; Wong, Peng Huwen; Kawahara, Seiichi; Tanaka, Yasuyuki

doi:10.1021/ma9816416

Cited by 6 publications

(6 citation statements)

References 17 publications

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“…The diad sequence distribution and isomeric unit (microstructure) contents, estimated from the intensity ratios, are tabulated in Table III, together with the content of 1,2 unit determined by 1 H NMR spectroscopy. The diad sequence distribution of trans-1,4, cis-1,4, and 1,2 units for PB, prepared by anionic polymerization using n-butyllithium, was random, as reported in our previous work, 28,29 The content of 1,2 unit for PB determined by 13 C NMR measurement was similar to that determined by 1 H NMR measurement. Consequently, the PB used in the present study was confirmed to have the same 1,2 unit content as one used in our previous work.…”

Section: Characterization Of Nr-sol Nr-gel and Pbsupporting

confidence: 82%

Lower Critical Solution Temperature Phase Behavior of Natural Rubber/Polybutadiene Blend

Kawahara

Asada

Isono

et al. 2002

Polym J

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ABSTRACT:The lower critical solution temperature (LCST) phase behavior of the blend of natural rubber (NR) with polybutadiene (PB) having 32.3% 1,2 unit was investigated by measuring T g through DSC after annealing the blend. NR was separated with toluene into branched polymer and crosslinked one as a soluble fraction (NR-sol) and gel fraction (NR-gel), respectively, followed by mixing with PB. Coexistence composition of NR-sol/PB and NR-gel/PB blends was determined by a method proposed in this work using DSC. The LCST of the NR-sol/PB blend was 328 K, being identical to the reported LCST of synthetic cis-1,4-polyisoprene/PB blend in our previous paper. The LCST of NR-gel/PB blend was quite similar to that of NR-sol/PB blend despite that NR-gel was crosslinked rubber (ν = 1.5 × 10 −6 ). Molecular weight was proved to produce no effect on the LCST phase behavior for high molecular weight polymer-polymer blend, i.e., NR/PB blend. KEY WORDS Natural Rubber / cis-1,4-polyisoprene / Polybutadiene / Blend / Miscibility / Lower Critical Solution Temperature (LCST) Phase Behavior / Miscibility and phase behavior of a pair of polymers, composed of carbon and hydrogen, is one of the most important phenomena to study the attractive forces 1-3 between dissimilar polymer chains, except for hydrogen bonding and charge transfer formations. To study these experimentally, a prudent selection of model polymers is important, because most high molecular weight hydrocarbons undergo crystallization or vitrification near ambient temperature, at which most experiments are carried out. We have investigated the miscibility and phase behavior for a blend of cis-1,4-polyisoprene (cis-1,4-PI) and polybutadiene (PB), which is regarded as liquid-like polymers, due to their low T g and T m 0 , i.e., below room temperature. In the previous study, 4 we found that PB with low 1,2 unit content was immiscible with cis-1,4-PI, whereas the reverse is found for PB with higher 1,2 unit content. The phase boundary between the miscible and immiscible state was at 32.3% 1,2 unit content, where the lower critical-solution-temperature (LCST) was observed to be 333 K for the blend. This phase transition was confirmed to take place reversibly and the mass transfer was proportional to the thermodynamic driving force, 5 T − T s , where T is the annealing temperature and T s is the spinodal temperature. Moreover, the extremely large negative excess volume on mixing 6 and free volume fraction apart from additive rule 7 were observed as well as a conformational change on mixing estimated from spin-lattice relaxation time measured by pulsed NMR spectroscopy. 8 These were proved positively by Roland, 9 Hasegawa, 10 Launger, 11 Bahani,12 and Roovers, 13 using various techniques respectively. However, the relationship between LCST and 1,2 unit content of PB, thus reported, was exclusively dependent upon the researchers. This was inferred to be due to the difference in molecular weight of the polymers, 12 despite that cis-1,4-PI and PB used in the previous works were hi...

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Section: Characterization Of Nr-sol Nr-gel and Pbsupporting

confidence: 82%

Lower Critical Solution Temperature Phase Behavior of Natural Rubber/Polybutadiene Blend

Kawahara

Asada

Isono

et al. 2002

Polym J

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“…The V units are isolated in the polymer chain. Signals diagnostic of the VV diads, expected in the region of the unsaturated carbons at 142.9 ppm and corresponding to the V 3 V carbons, are not detected even at high butadiene molar fractions. , Recent results on the characterization of anionic PBD samples containing similar vinyl content confirm that the formation of the VV diad is a scarcely probable event . In the sPS−B copolymers isolated V units are observed in the SVS (lines 2 and 3), CVC (lines 5, 20, 23, and 36), and CVT (line 16) sequences.…”

Section: Resultsmentioning

confidence: 92%

“…17,18 Recent results on the characterization of anionic PBD samples containing similar vinyl content confirm that the formation of the VV diad is a scarcely probable event. 19 In the sPS-B copolymers isolated V units are observed in the SVS (lines 2 and 3), CVC (lines 5, 20, 23, and 36), and CVT (line 16) sequences. Monomer triads including V were also identified in VCV (lines 13, 18, 22, and 37) and CCV (lines 27 and 36) triads.…”

Section: Resultsmentioning

confidence: 95%

Structural Characterization of Novel Styrene−Butadiene Block Copolymers Containing Syndiotactic Styrene Homosequences

et al. 2002

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Samples of poly(syndiotactic styrene-co-butadiene) (sPS-B) have been prepared using methylalumoxane (MAO) activated CpTiCl3 under a range of experimental conditions. Copolymerization activities were low (24-36 kg mol -1 of cat. h -1 ) and nearly constant over the range of polymerization temperatures investigated (25-70 °C). Eight sPS-B samples were synthesized at 25 °C with styrene molar fractions (xs) covering a full range of compositions (xs ) 0.15-0.92). The copolymer samples were characterized by solution and solid state 13 C NMR spectroscopy, X-ray powder diffraction analysis, and thermal (DSC) analysis. The 13 C NMR analysis of the copolymer microstructure suggests that the butadiene homosequences are primarily cis-1,4 and the styrene segments are syndiotactic. However, some 1,2-and trans-1,4-butadiene units are occasionally formed during the polymerization process. The 13 C NMR resonances diagnostic of the monomer triads comprising styrene units (SSB, SBS, BBS, BSB, and SSS) were assigned and the average styrene block lengths (nS) calculated. Copolymer samples in which nS > 9 are crystalline due to the syndiotactic polystyrene segments detected in the δ-toluene clathrate form with melting points in the range 205-230 °C. Syndiotactic polystyrene segments with shorter styrene block lengths are amorphous and partially included in the poly(butadiene) rubber domains. TEM images of sample 13 (xS ) 0.37, nS ) 8.8) show the presence of small sPS fibers.

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“…Thus, the SEC measurement was performed to determine the molecular weight of PS, after ozonolysis of DPNR-graft-PS. In our previous works, it was ensured that signals, assigned to carbon-carbon double bonds, disappeared in the NMR spectrum after ozonolysis of DPNR-graft-PS [15,19,20]. This was explained to be due to the cleavage of all carbon-carbon double bonds of natural rubber with ozone.…”

Section: Observationmentioning

confidence: 97%

Frozen non-equilibrium structure for anisotropically deformed natural rubber with nanomatrix structure observed by 3D FIB-SEM and electron tomography

et al. 2015

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Abstracts Effect of frozen non-equilibrium structure for anisotropically deformed natural rubber with the nanomatrix structure on mechanical properties was investigated with respect to morphology analysis through 3D observation. Natural rubber with the nanomatrix structure was prepared by graft copolymerization of styrene onto natural rubber particles in latex stage followed by coagulation of the resulting latex. The morphology was observed by electron tomography and focused ion beam-scanning electron microscopy (FIB-SEM). The nanomatrix structure in isotropic state was precisely analyzed by electron tomography and synchrotron scattering technique. The nanomatrix structure was found to consist of natural rubber particles and polystyrene nanoparticles. The frequency-independent loss tangent at plateau region was attributed to the discontinuous nanomatrix structure. After annealing at 403 K and 7 MPa, the nanomatrix became continuous, which resulted in the increases in stress at strain of one and storage modulus as well as increase in loss tangent.

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

Cited by 6 publications

References 17 publications

Lower Critical Solution Temperature Phase Behavior of Natural Rubber/Polybutadiene Blend

Lower Critical Solution Temperature Phase Behavior of Natural Rubber/Polybutadiene Blend

Structural Characterization of Novel Styrene−Butadiene Block Copolymers Containing Syndiotactic Styrene Homosequences

Frozen non-equilibrium structure for anisotropically deformed natural rubber with nanomatrix structure observed by 3D FIB-SEM and electron tomography

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