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See detailSynthesis and thermal properties of linear amphiphilic diblock copolymers of L-lactide and 2-dimethylaminoethyl methacrylate
Kryuchkov, Maksym A.; Detrembleur, Christophe ULg; Jérôme, Robert ULg et al

in Macromolecules (2011), 44(13), 5209-5217

A well-defined series of nine poly(l-lactide)-b-(2-dimethylaminoethyl methacrylate) (PLLA-b-PDMAEMA) linear diblock copolymers with low polydispersity were prepared by ring-opening polymerization of LLA ... [more ▼]

A well-defined series of nine poly(l-lactide)-b-(2-dimethylaminoethyl methacrylate) (PLLA-b-PDMAEMA) linear diblock copolymers with low polydispersity were prepared by ring-opening polymerization of LLA using 4-isopropylbenzyl alcohol and tin octoate as the initiating system, conversion of the OH-terminated PLLA into Br-terminated macroinitiators (5, 13, and 19 kg/mol), followed by atom transfer radical polymerization of DMAEMA (to obtain one-half, equal, and twice the molecular weight of each PLLA block). Compositional analysis and molecular weight characterization were done using NMR, SEC–LS, TGA, polarimetry, and PDMAEMA quaternization/precipitation to test for residual PLLA homopolymer. DSC investigations indicate that low molecular weight amorphous PLLA or PDMAEMA blocks (less than or equal to ca. 5000 g/mol) are miscible in the second block. Compared to the parent PLLA homopolymers, PLLA crystallization in the block copolymers is significantly retarded, whereas the degree of crystallinity is only mildly affected and melting points are reduced only for the low molecular weight miscible blocks. [less ▲]

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See detailStereocomplexation and morphology of polylactides
Brochu, Sylvie; Prud'homme, Robert E; Barakat, Ibrahim et al

in Macromolecules (1995), 28(15), 5230-5239

Blends of isotactic polylactides of opposite configurations lead to the formation of stereocomplexes, provided the enantiomeric excess of the two homopolymers in contact is high enough. In this study, the ... [more ▼]

Blends of isotactic polylactides of opposite configurations lead to the formation of stereocomplexes, provided the enantiomeric excess of the two homopolymers in contact is high enough. In this study, the stereocomplex formation between a poly(L-lactide) (100L) having an enantiomeric excess of 100% and a poly(D-lactide) having an enantiomeric excess of 80% (80D) has been investigated using differential scanning calorimetry and optical microscopy. These results have been compared to those obtained between two polylactides having both an enantiomeric excess of 100% (100L/100D blend). The melting temperatures of blends 100L/100D and 100L/80D are 230 and 208 degrees C, respectively. In both cases, the stereocomplex formation is preferred to the homopolymer crystallization and the stereocomplex controls the morphology of the blends over a wide range of concentrations. However, this control is more rigorous when the D component is 100% isotactic. This difference leads to a more complete crystallization of homopolymer 100L and to a greater influence of crystallization conditions in 100L/80D blends in comparison with 100L/100D blends. An epitaxial crystallization between the homopolymer 100L and the stereocomplex 100L/80D has also been observed at certain compositions. [less ▲]

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See detailSynthesis, characterization, and miscibility of caprolactone random copolymers
Vion, Jean-Marc; Jérôme, Robert ULg; Teyssié, Philippe et al

in Macromolecules (1986), 19(7), 1828-1838

The ring-opening polymerization and copolymerization of ε-caprolactone, ε-methyl-ε-caprolactone, β,δ-methyl-ε-caprolactone (mixed isomers), and L-lactide using aluminum isopropoxide as initiator were ... [more ▼]

The ring-opening polymerization and copolymerization of ε-caprolactone, ε-methyl-ε-caprolactone, β,δ-methyl-ε-caprolactone (mixed isomers), and L-lactide using aluminum isopropoxide as initiator were investigated. The chain propagation proceeds through a living anionic type coordinated insertion mechanism. The kinetic features of this process are reported. The experimental monomer reactivity ratios indicate that ε-caprolactone and its methyl derivatives yield random copolyesters. However, the ε-caprolactone/L-lactide pair exhibits a departure from randomness with the preferred incorporation of L-lactide units. The thermal properties of the copolymers were investigated by differential scanning calorimetry. It was found that the crystallization of ε-caprolactone units is limited, in all cases, to copolymers which are rich in this sort of unit. At the same time, the crystallization of L-lactide units was observed in copolymers with high concentrations of this comonomer. Analysis of the melting point depreasion data of the copolymers indicates that the L-lactide units are almost completely rejected from the caprolactone crystals, whereas about 50% of the ε-methyl-ε-caprolactone and δ,δ-methyl-ε-caprolactone comonomer units are incorporated into the ε-caprolactone crystals due to an obvious structural similarity. Finally, poly(ε-caprolactone-co-ε-methyl-ε-caprolactone) samples are miscible with poly(viny1 chloride) (PVC) whatever the composition of the copolymer and the composition of the blend, whereas poly(εt-caprolactone-co-L-lactide) samples are miscible with PVC uniquely for copolymer L-lactide contents equal to or smaller than 40 wt %. In all cases where miscibility was found, a negative thermodynamic interaction parameter was computed. [less ▲]

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