Stiff and hierarchical chain nature of atactic and stereoregular poly(substituted methylene)s

Shikinaka, Kazuhiro; Suzuki, Kenta; Masunaga, Hiroyasu; Ihara, Eiji; Shigehara, Kiyotaka

doi:10.1002/pi.5532

Cited by 12 publications

(10 citation statements)

References 36 publications

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“…These numbers suggest that the polycarbene backbones are highly extended rather than coiled, as recently described for atactic homopolymers of benzyl diazoacetate. 38 Note also that compared to the corresponding homopolymer segments, the block copolymer appears to have similar thermal stability in air up to ~260 °C (SI, Figure S26).…”

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confidence: 95%

“…The end-to-end distance of the fully stretched out block copolymers of DP ∼ 175 (based on Figure C and relative ratio of two blocks) is estimated to be 220 Å (“End-to-End Distance” section, SI), which translates to a d -spacing of 440 Å. These numbers suggest that the polycarbene backbones are highly extended rather than coiled, as recently described for atactic homopolymers of benzyl diazoacetate . Note also that compared to the corresponding homopolymer segments, the block copolymer appears to have similar thermal stability in air up to ∼260 °C (SI, Figure S26).…”

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confidence: 99%

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A Dinuclear Mechanism Implicated in Controlled Carbene Polymerization

et al. 2019

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Carbene polymerization provides polyolefins that cannot be readily prepared from olefin monomers; however, controlled and living carbene polymerization has been a long-standing challenge. Here we report a new class of initiators, (π-allyl)palladium carboxylate dimers, which polymerize ethyl diazoacetate, a carbene precursor in a controlled and quasi-living manner, with nearly quantitative yields, degrees of polymerization >100, molecular weight dispersities 1.2-1.4, and well-defined, diversifiable chain ends. This method also provides block copolycarbenes that undergo microphase segregation. Experimental and theoretical mechanistic analysis supports a new dinuclear mechanism for this process.

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confidence: 95%

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A Dinuclear Mechanism Implicated in Controlled Carbene Polymerization

et al. 2019

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“…Although it is an amorphous polymer, the peak corresponding to amorphous hallo provides insight into the packing structure. [ 41–43 ] The peak position in the lowest q range is 6.4 nm −1 , which corresponds to 0.98 nm. This reflects the cross‐sectional radius of the polymer chain, including the bulky side chain.…”

Section: Resultsmentioning

confidence: 99%

Characteristic Features of α and β Relaxations of Poly(diethyl fumarate) as the Poly(substituted methylene)

Suzuki

Tsuji

Miyata

et al. 2021

Macro Chemistry & Physics

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Recently the β relaxation draws attention because it may act as a precursor of the α relaxation and potentially influences a wide range of properties. In many cases, the weak intensity of the β relaxation limits the experimental investigation. Herein, the β relaxation of poly(diethyl fumarate) (PDEF) using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and dielectric spectroscopy is investigated. Originating from the absence of methylene spacer in the main chain, polyfumarates possess an intense β relaxation. Unlike common vinyl polymers, PDEF shows two distinct steps in DSC measurement corresponding to α and β relaxations. Interestingly, the relative intensities of α and β relaxations depend on the thermal history. The β relaxation of PDEF obtained by dielectric spectroscopy at high temperature is similar to that of poly(methyl methacrylate) (PMMA). However, the β relaxation of PDEF follows the VFT equation rather than the Arrhenius equation at low temperatures. The analysis of PDEF/PMMA blend suggests the local orientation of PDEF chain plays a vital role in the intense β relaxation.

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“… 47 Subsequent studies by Tokita, Shikinaka, Ihara, and co-workers confirmed that PEA and related syndiotactic polymers of diazoacetates show thermotropic liquid crystalline behavior due to a rod-like helical conformation in the polymer backbone. 48 − 50 The syndiotactic polymer pM 5 is likely to form similar triple helices, and the forces keeping the aggregates together are likely to be stronger in such triple-helix aggregates than in the atactic material, leading to a lower LCST for the syndiotactic polymer than for the atactic material ( Figure 6 , bottom). Solvation into individual polymer chains in solution is enthalpy-driven, while formation of aggregates at higher temperature is an entropy-driven process, releasing water solvent molecules upon aggregation of the individual solvated polymer chains.…”

Section: Resultsmentioning

confidence: 99%

Aqueous Phase Separation Behavior of Highly Syndiotactic, High Molecular Weight Polymers with Densely Packed Hydroxy-Containing Side Groups

et al. 2018

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Herein we describe the Rh-catalyzed C1 polymerization of silyl-protected diazoacetates of the general formula HC(=N2)C(=O)O(CH2)xOSiR3, where x = 2–5. After polymerization and subsequent desilylation, syndiotactic polymers bearing a hydroxy-containing side group on every backbone carbon are obtained. The molecular weight of the desired polymers can be controlled via chain transfer with methanol during the polymerization. The produced polymers are compared to atactic analogues formed by [(η3-C3H5)PdCl]-catalyzed polymerization of silyl-protected diazoacetates with the same general formula. While the polymers produced by the Rh and Pd catalysts have the same hydrophilic/hydrophobic balance, the stereoregularity of the polymers formed by the Rh catalyst was found to be of influence on the thermoresponsive behavior of the polymer. The effect of this stereoregularity on the thermoresponsive phase separation behavior of the produced polymers in aqueous solution was investigated.

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Stiff and hierarchical chain nature of atactic and stereoregular poly(substituted methylene)s

Cited by 12 publications

References 36 publications

A Dinuclear Mechanism Implicated in Controlled Carbene Polymerization

A Dinuclear Mechanism Implicated in Controlled Carbene Polymerization

Characteristic Features of α and β Relaxations of Poly(diethyl fumarate) as the Poly(substituted methylene)

Aqueous Phase Separation Behavior of Highly Syndiotactic, High Molecular Weight Polymers with Densely Packed Hydroxy-Containing Side Groups

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