Thermoelastic properties of chemical copolymers

Mark, J. E.

doi:10.1002/pol.1974.180120615

Cited by 8 publications

(4 citation statements)

References 17 publications

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“…The small differences between some observed resonances and the chemical shifts calculated for the methyl and P methine carbons in P-VC (see Figures 4 and 5) are due to minor imperfections in the RIS model for P-VC. 18 Methine carbons C*HC1 belonging to VC units adjacent to P units (see Figure 2) resonate downfield from or partially overlap the downfield methine resonances in long VC sequences (see Figure 3b). Chemical shifts calculated for C*HC1 carbons show the opposite behavior and are predicted to resonate slightly upfield from the PVC-like methine carbons.…”

Section: Resultsmentioning

confidence: 99%

Carbon-13 NMR chemical shifts and the microstructure of propylene-vinyl chloride copolymers with low propylene content

Tonelli¹,

Schilling²

1984

Macromolecules

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13C NMR chemical shifts expected for the carbon atoms in propylene-vinyl chloride (P-VC) copolymers of low propylene content are calculated as a function of copolymer stereosequence. Mark's conformational model of P-VC copolymers is coupled with the -gauche effect, which results in upfield chemical shifts for those carbon atoms in a gauche arrangement with carbon or chlorine substituents in the position, to calculate the 13C NMR chemical shifts of the carbon atoms in the vicinity of a propylene unit surrounded by vinyl chloride units. Agreement between the calculated chemical shifts and those we observe in the 50-MHz 13C NMR spectrum recorded for a P-VC copolymer containing 5 mol % propylene units is excellent. As an example, the chemical shifts calculated for the CH3 carbons are sensitive to pentad but not to heptad or longer stereosequences. This is confirmed in the 13C NMR spectrum of our P-VC copolymer with low P content and contrasts with the predicted and observed heptad sensitivity of the CH3 resonances in the 13C NMR spectra of atactic polypropylene. The agreement achieved between calculated and observed chemical shifts for our P-VC copolymer enables us to assign its 13C NMR spectrum, to evaluate the statistics of stereochemical placements during the copolymerization of P with VC monomers, and to compare these stereochemical statistics to those resulting from the homopolymerization of P and VC.

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Section: Resultsmentioning

confidence: 99%

Carbon-13 NMR chemical shifts and the microstructure of propylene-vinyl chloride copolymers with low propylene content

Tonelli¹,

Schilling²

1984

Macromolecules

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“…This scheme for characterizing the stereochemical structure of PMPS chains is identical to that used for the extensively studied vinyl class of polymers. The isotactic, syndiotactic, and atactic classifications apply to both monosubstituted vinyl chains [CHR-CH2-], [2][3][4][5][6][7][8][9][10][11] and disubstituted vinyl chains [CRR' -CH-1,. 1 2 9 1 3 Because of the wealth of information obtained on vinyl polymers, the effect of stereochemical composition on their statistical properties is now quite well understood.…”

Section: Introductionmentioning

confidence: 99%

“…and the C-C-C skeletal bond angles are relatively small (110-122 0 ). [2][3][4][5][6][7][8][9][10][11][12][13]…”

Section: Introductionmentioning

confidence: 99%

Random‐coil dimensions of poly(methylphenylsiloxane) and their dependence on stereochemical structure

Mark

1975

J. Polym. Sci. Polym. Phys. Ed.

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Rotational isomeric state theory was used to study the unperturbed dimensions 〈r2〉0 of poly(methylphenylsiloxane) (PMPS) chains [Si(CH3)(C6H5)O]x as a function of their stereochemical structure. The required conformational energies were obtained from semi‐empirical, interatomic potential energy functions and from known results on poly(dimethylsiloxane). PMPS chains were found to differ from monosubstituted and disubstituted vinyl chains primarily in the larger distance of separation between groups in conformations giving rise to “pentanetype interactions.” In PMPS, the relatively large distance of separation, 3.8 Å, makes such in teractions attractive, particularly in the case of two phenyl groups; in contrast, such interactions are strongly repulsive at the ∼2.5 Å separation characterizing vinyl chains. According to the calculated results, PMPS chains are very different from vinyl chains in that increase in isotacticity should cause a significant decrease in 〈r2〉0 and increase in d ln 〈r2〉0/dT. Comparison of theory with experimental results in the literature suggests that PMPS polymers which have been studied in this regard must have been significantly syndiotactic in stereochemical structure.

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“…*O Estimates obtained from the densities of polymer, silica, and filled network are seen to be smaller than those obtained directly from the increase in weight of the network. This indicates that either the filler particles have not been completely converted to silica or the particles contain a significant number Isotherms for PDMS networks prepared using TEOS to simultaneously endlink hydroxyl-terminated chains (21.3X 103 g mol-I) and to provide filler upon its hydrolysis.20 For samples 1-7, the filler thus incorporated amounted to 0.0,2.28,4.56,6.75,8.83, 10.8 and 14.6 wt %, respectively. Additional information on these samples is given in Figs 8 and 9.…”

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confidence: 99%

Bimodal networks and networks reinforced by the in situ precipitation of silica

Mark

1985

Brit. Poly. J.

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The goal of primary interest in these investigations was the development of novel methods for preparing elastomeric networks having unusually good ultimate properties. The first technique employed involves endlinking mixtures of very short and relatively long functionally‐terminated chains to give bimodal networks. Such (unfilled) elastomers show very large increases in reduced stress or modulus at high elongations because of the very limited extensibility of the short chains present in the networks. The second technique employs the in situ precipitation of reinforcing silica either after, during, or before network formation. The reaction involves hydrolysis of tetraethylorthosilicate, using a variety of catalysts and precipitation conditions, and the effectiveness of the technique is gauged by stress‐strain measurements carried out to yield values of the maximum extensibility, ultimate strength, and energy of rupture of the filled networks. Information on the filler particles thus introduced is obtained from density determinations, light scattering measurements, and electron microscopy.

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Thermoelastic properties of chemical copolymers

Cited by 8 publications

References 17 publications

Carbon-13 NMR chemical shifts and the microstructure of propylene-vinyl chloride copolymers with low propylene content

Carbon-13 NMR chemical shifts and the microstructure of propylene-vinyl chloride copolymers with low propylene content

Random‐coil dimensions of poly(methylphenylsiloxane) and their dependence on stereochemical structure

Bimodal networks and networks reinforced by the in situ precipitation of silica

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