Marie-France Llauro

Morphology control of polyester-polyolefin blends by transesterification during processing operations in the presence of dibutyltin oxide

PE and PBT are known to be incompatible polymers. A grafted copolymer PBT-EVA has been generated as a compatibilizer in situ during the processing operation by redistributive transesterification between PBT and EVA in the presence of dibutyl tin oxide (DBTO). This copolymer has been isolated by selective extractions from PBT/EVA/DBTO (49.5/49.5/1% in weight) blend after processing in the melt. It has been evidenced by a 1H-NMR study. This copolymer presents all the resonances of PBT and EVA sequences and some others that have been assigned specificaly to grafting. To achieve these assignments, a model compound obtained by transesterification of EVA with methyl benzoate has been used. When the melt conditions enable synthesis of the grafted copolymer PBT-EVA in situ during processing operations, important changes in the morphology of PE/PBT/EVA/DBTO blends are observed. SEM analysis shows a decrease of PBT particle size and a good adhesion between the PBT and PE phase.

Properties of PETG/EVA blends: 2. Study of reactive compatibilization by n.m.r. spectroscopy and linear viscoelastic properties

Abstract The reaction product of both methylbenzoate and dimethylphthalate with dibutyltin oxide was determined to be an 1-alkoxy-3-acyloxy distannoxane by multinuclear n.m.r. spectroscopy (1H, 13C and 119Sn) in solution. Dibutyltin oxide promotes ester interchange reactions. It was used to compatibilize the immiscible blend of polyethylene terephthalate glycol (PETG) with the ethylene vinyl acetate (EVA) copolymer. The linear viscoelastic properties of the compatibilized blend were determined and analysed in light of the n.m.r. results.

Existence of an intradimeric rearrangement in monofunctional tetrabutyldistannoxanes [Bu4Sn2X2O]2 probed by multinuclear NMR spectroscopy in solution and in solid state

Abstract A set of 1-D and 2-D, 13 C- and 119 Sn-NMR experiments—both in solution and in the solid state—exhibit a common peculiarity of the monofunctional tetrabutyldistannoxanes of general formulae R 4 Sn 2 X 2 O in comparison with the no problematic NMR data of difunctional tetrabutyldistannoxanes R 4 Sn 2 XYO. Relying on the support of these observations, the existence of a dynamic process is evidenced in solution. This process, rapid and equilibrated at ambient temperature, is shown to be frozen both in solution at 188 K and in the solid state. A mechanism of intramolecular rearrangement of the distannoxane dimeric form is discussed on the basis of modelisation of the movements required. It accounts for all spectroscopic observations and is not expected to occur with the dimer form of the difunctional distannoxanes (X≠Y).

Multinuclear NMR Characterization of Co-cross-linking of Ethylene-co-vinylacetate and Ethylene-co-methylacrylate Polymer Blends in the Presence of Dibutyltin Oxide

Abstract The co-cross-linking reaction of ethylene-co-vinylacetate (EVA) and ethylene-co-methylacrylate (EMA) polymer blends in the presence of dibutyltin oxide in the molten state is an interchain redistributive transesterification (ester-ester interchange reaction). It is shown with model esters, namely n-octyl acetate (1) and methyl nonanoate (2) in solution, that the efficientcatalytic species are 1,3-acyl, alkoxy distannoxane from the reaction of esters with dibutyltin oxide. An intermolecular dimeric rearrangement between acyl and alkoxy dimeric distannoxanes from (1) and (2) esters occurs at ambient temperature without ligand exchange. Ligand exchange on tin atoms by reactions between free ester (1) and dimeric distannoxane occurs at higher temperature at both acyloxy and alkoxy tin sites. Reactions are characterized by multinuclear NMR spectroscopy (1H, 13C, 119Sn). Tetra acyloxy or tetra alkoxy distannoxanes are also efficientcatalysts for this redistributive transesterification.

Analogous reaction for maximum sulfonation of polysulfones

SummaryThe sulfonation of the model compounds of the structural units of the polysulfones and bis phenol A polyethersulfones has been conducted up to completion using SO3 in a dichloroethane solution at room temperature. Whatever the initial structure may be, only one sulfonic group per aromatic ring can be attached. Water soluble polymers with the same degree of sulfonation can be prepared, without chain scission.

Radical-initiated copolymers of N-vinyl pyrrolidone and N-acryloxy succinimide: kinetic and microstructure studies

Abstract Kinetics of solution (co)polymerization of N-vinyl pyrrolidone (NVP, or V) and N-acryloxy succinimide (NAS, or A) have been investigated at 60°C in N, N-dimethylformamide with 4,4′-azobis(4-cyanopentanoic acid) as initiator. First, the k p √k i value for homopolymerization of A monomer was estimated as 0.87 10.5 mol−0.5 s−0.5. The comonomer feed composition was observed to have a strong effect on the overall copolymerization rate. Reactivity ratios of the binary system were determined to be rNAS = 0.27 ± 0.04 and rNVP = 0.01 ± 0.01, indicating a strong alternating tendency in the formed copolymer. Copolymers were then characterized as regards to composition (by ultraviolet spectrophotometry) and monomer sequence distribution (by 13C nuclear magnetic resonance spectroscopy). The presence of a small fraction of VVA triads was clearly evidenced which was not expected from simulation based on a terminal kinetic model; the occurrence of a more complex model has been discussed.

Hydrogen-bonded complexes of pentaalkyl guanidines

The hydrogen-bonded complexes of strongly basic pentaalkylguanidines (G) with 4-fluorophenol as a proton donor reference (FP) have been studied in CDCl3 solution by means of 13C NMR spectroscopy. The equilibrium constants for formation and the chemical shifts of all the 13C NMR lines of the hydrogen-bonded complexes were determined. This rich spectroscopic characterization of the complexes allowed us to discuss their structure. The guanidines were found to be more basic than triethylamine, the bicyclic ones being the strongest bases, in accordance with expectations. The ion pair character of the hydrogen-bonded complexes was as high as 40% for the strongest bases. In addition to the expected GFP complex, a diassociation complex G(FP)2 was observed at high fluorophenol concentrations. In this latter complex, one fluorophenol molecule is ionized by full proton transfer to the guanidine and the second fluorophenol molecule is bound by hydrogen bonding to the fluorophenate anion. A linear relationship between the 13C NMR chemical shift variations of 4-fluorophenol and log(K1) was found, as in the original work of Gurka and Taft using 19F NMR.

Reaction of dibutyltin oxide with amides in presence of traces of water: multinuclear NMR study and mechanism

Abstract The product of the reaction of primary and secondary amides with dibutyltin oxide is shown to be a dimeric 1,3-diacyloxytetrabutyldistannoxane. The reaction was studied in bulk with model amides at 180°C, avoiding perfect anhydrous conditions, in view to be transposable to transamidification with reactive extrusion process. The formation of an intermediate compound of the type 1-acyloxy-3-alkylaminotetrabutyldistannoxane is pointed out. With an excess of amide, the presence of water leads to the dimeric 1,3-diacyloxytetrabutyldistannoxane. Without an excess of amide, the hydrolysis of this intermediate leads to a more complex tetrastannoxane structure associated in a more or less perfect ladder-like structure including partially hydrolyzed and condensed forms of the distannoxane. The dimeric 1-acyloxy-3-alkoxytetrabutyldistannoxanes resulting from the reaction of esters with dibutyltin oxide are shown to give a similar stannoxane structure after hydrolysis. All the products were characterized in solution by 1 H-, 13 C- and 119 Sn-NMR spectroscopy. On the basis of the spectroscopic analysis, a mechanism of the reaction is proposed and discussed.

Aluminium and rare earths alkoxides as initiators for the heterogeneous anionic coordinated polymerisation of propylene oxide. A 1H NMR approach of the regioselectivity and transfer ability of the catalytic system

In order to outline the placement of the monomer units during the heterogeneous anionic coordinated polymerization of propylene oxide, the regioselectivity of the first monomer insertion at the initiator was examined by 1 H NMR. To start, aluminium benzyl oxide chemically grafted onto a porous support was used as initiator. It was shown that the regioselectivity of the first insertion reflects the placement of the monomer units in the chain. Although there is no direct correlation between these two parameters, a knowledge of the regioselectivity of this first insertion allowed us to compare different catalytic systems. With aluminium alkoxides as initiators, both carbon atoms are attacked at random in the first insertion step. Adding triethylamine increases notably the regioselectivity. The replacement of aluminium by zirconium or a rare earth element gives about the same percentage of regular insertion as that obtained with the complex aluminium alkoxide-NEt 3 . On the other hand, the allyl double bond content was measured and the values of the transfer constant were deduced. Adding triethylamine to aluminium alkoxides or using Zr and rare earth based systems causes a decrease of the transfer constant. The more regular the PO insertion is, the lower is the transfer constant.

13C-NMR of Anionic Low-Molecular-Weight Stat-Poly(Ethylene Oxide-Co-Propylene Oxide): Correlation with Monte Carlo Simulation

Abstract Low-molecular-weight stat-poly(ethylene oxide-co-propylene oxide) copolymers have been prepared by anionic way using a new heterogeneous catalytic process. After checking the reactivity ratios of the system, the new resonance peaks due to low-molecular-weight chains (end groups) have been assigned and the copolymers were fully characterized by 13C-NMR in terms of triads centered in ethylene oxide units. Finally, signal areas have been successfully compared with computer simulation based on the Monte Carlo method, taking into account the chain length distribution resulting from anionic polymerization.