Structural irregularities in poly(vinyl alcohol)

Adelman, Robert L.; Ferguson, Raymond C.

doi:10.1002/pol.1975.170130409

Cited by 28 publications

(8 citation statements)

References 33 publications

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“…One of the main reasons for the broadening is most probably the accumulation of the less reactive primary C-SC(S)OR 0 terminal originating from the head-to-head addition, which is inherent in the VAc radical polymerization. [44][45][46][47][48] These results suggest that Mn 2 (CO) 10 induces the controlled/living radical polymerization of VAc even in conjunction with a xanthate via the reversible activation of the C-SC(S)OR terminal.…”

Section: Measurementsmentioning

confidence: 75%

Mn2(CO)10-Induced RAFT Polymerization of Vinyl Acetate, Methyl Acrylate, and Styrene

2009

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A dinuclear manganese complex [Mn 2 (CO) 10 ] induced the controlled/living radical polymerization of various conjugated and unconjugated vinyl monomers including vinyl acetate, methyl acrylate, and styrene in conjunction with dithiocarbonyl compounds [R-SC(S)Z] under weak visible light at 40 C. The obtained polymers had controlled molecular weights, narrow molecular weight distributions, and well-defined chain-end groups originating from R-SC(S)Z, as indicated by SEC, 1 H NMR, and MALDI-TOF-MS analyses. The polymerization most probably proceeds via the reversible activation of the C-SC(S)Z bond by Á Mn(CO) 5 via the metal-catalyzed process and/or by the carbon-centered radical species via the additionfragmentation chain transfer (RAFT) process.KEY WORDS: Vinyl Acetate / Acrylate / Styrene / Living Radical Polymerization / RAFT Polymerization / Manganese Complex / Various aspects of the controlled/living radical polymerization have been significantly developed in this decade, including a variety of initiating systems, controllable monomers, polymer structures, fusion with other substances, and applications to functional materials. Among the numerous initiating systems, there are now three representatives in terms of wide applicability and good controllability; i.e., the nitroxide-mediated radical polymerization (NMP), 1,2 metal-catalyzed living radical polymerization or atom transfer radical polymerization (ATRP), [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] and reversible addition-fragmentation chain transfer (RAFT) 18 polymerization or macromolecular design via interchange of xanthate (MADIX). 19 Although the components and the mechanisms are different, they are all based on the reversible transient activation of the dormant covalent species into the growing radical species. However, each system has its own characteristics or features due to the differences, which suggests that the choice of initiating systems is important depending on the monomers, conditions, purposes, etc.The metal-catalyzed living radical polymerization or ATRP is one of the best methods in terms of the well-defined architecture of the polymers from a variety of conjugated monomers, such as methacrylates, acrylates, acrylamides, acrylonitrile, and styrenes. This polymerization is generally initiated by the carbon radical generated from the alkyl halide upon the activation of the carbon-halogen bond by the transition metal catalyst, and then proceeds via the metalcatalyzed reversible activation of the carbon-halogen terminal into the growing radical species. One growing polymer chain end is thus generated from one carbon-halogen bond, which can permit the well-defined polymer synthesis. Although various transition metals, such as ruthenium, 3 20 The choice of the metal complexes including metals and ligands as well as the halides is important for the precise control of the polymerizations depending on the monomers.In contrast, the RAFT/MADIX system with the dithiocarbonyl compounds [R-SC(S)Z] is one of the most widely applica...

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Section: Measurementsmentioning

confidence: 75%

Mn2(CO)10-Induced RAFT Polymerization of Vinyl Acetate, Methyl Acrylate, and Styrene

2009

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“…A second important mechanism leading to long branches is the insertion in propagating living chains of dead chains with terminal double bonds, being created by transfer to monomer or disproportionation termination. This terminal double bond (TDB) propagation has been mainly addressed in the context of PVAc studies [6][7][8][9][10][11][12][13][14][15][16][17][18][19] and somewhat less in ldPE work. 21 In the present modeling study, we will focus on the impact of the combination of the two branching mechanisms, transfer to polymer and terminal double bond propagation, on the MWD.…”

Section: Introductionmentioning

confidence: 99%

Molecular Weight Distribution Modeling of Radical Polymerization in a CSTR with Long Chain Branching through Transfer to Polymer and Terminal Double Bond (TDB) Propagation

2002

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The modeling of free radical polymerization with long chain branching in a CSTR is addressed. Long branches are assumed to be created by transfer to polymer and by insertion of active terminal double bonds (TDBs). Such TDBs may be produced by transfer to monomer and termination by disproportionation. The modeling approach is based on population balances being solved using a Galerkin finite element method (FEM). Two different models have been derived. The “TDB classes” model employs different equations for each class of chains with a certain number of TDBs. The “TDB moment distribution” uses the pseudodistribution method developed by us before22 for simultaneous molecular weight/degree of branching distribution modeling. Model calculations have been performed for the case of poly(vinyl acetate) (PVAc). In the case of the maximum one TDB per chain, the two models prove to be mathematically equivalent. An increase of TDB propagation rate leads to a broadening of chain length distribution (CLD) and sometimes to a more pronounced “shoulder” at long chain lengths. The significant concentration range extends to extremely long chain lengths (1010)well within a gel regimebut the model could fully cover this. Quite remarkably, concentrations of living chains are higher than those of dead chains in this region. The average number of TDBs per chain could be calculated and turns out to be constant at shorter chain lengths, but becomes lower for longer chains. This is explained by the combined action of chain growth by TDB propagation, which implies TDB consumption as well, and transfer to polymer. For the case of more than one TDB per chain, the two models yield different results depending on closure relationships. The TDB moment distribution model revealed that the longest chains carry tens of thousands of TDBs. The classes model strongly underestimates the number of TDBs and hence the reactivity of the dead chains to TDB propagation. The results show the effect of dead chains with many TDBs acting as cross-linkers for living chains. As an interesting trend, it was observed that with increasing TDB propagation rate an increasing fraction of monomer units existing in polymer chains is present in fewer, but extremely long living, chains.

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“…This is in the range found by chemical methods for similar poly(vinyl alcohol) samples. 6 Two weak resonances at 38.5 and 39 ppm are tentatively assigned to methylene carbon atom 3, with a predicted chemical shift of 42.0 ppm. Other weak, and as yet unidentified, resonances fall in the region 39-42 ppm.…”

Section: Resultsmentioning

confidence: 97%

Microstructure of poly(vinyl alcohol) by 100-MHz carbon-13 NMR

Ovenall¹

1984

Macromolecules

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The microstructure of atactic and highly isotactic poly(vinyl alcohol) samples has been studied by 100-MHz carbon-13 NMR spectroscopy. Resolution-enhanced spectra show sensitivity to heptad and hexad tactic sequences. The highly isotactic sample obeys first-order Markov statistics while the atactic sample is Bernoullian. Spectra taken in Me2SO-d6 and in D20 as solvents show marked differences, which may be due to conformation changes. Weak features, arising from reversed monomer sequences and other structural irregularities, have been identified in the spectrum of the atactic sample. A spin-echo NMR experiment with gated decoupling was used in the assignment of these weak features.

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Structural irregularities in poly(vinyl alcohol)

Cited by 28 publications

References 33 publications

Mn2(CO)10-Induced RAFT Polymerization of Vinyl Acetate, Methyl Acrylate, and Styrene

Mn2(CO)10-Induced RAFT Polymerization of Vinyl Acetate, Methyl Acrylate, and Styrene

Molecular Weight Distribution Modeling of Radical Polymerization in a CSTR with Long Chain Branching through Transfer to Polymer and Terminal Double Bond (TDB) Propagation

Microstructure of poly(vinyl alcohol) by 100-MHz carbon-13 NMR

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