A neutron scattering investigation of the transesterification of a main-chain aromatic polyester

MacDonald, William; McLenaghan, A. D. W.; Mclean, G. A.; Richards, Roy J.; King, Stephen M.

doi:10.1021/ma00023a017

Cited by 53 publications

(26 citation statements)

References 5 publications

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“…The possibility of an ester‐interchange reaction was investigated using NMR. An ester‐interchange reaction is rapid in the melt stage at high temperature 24–26. The ester‐interchange reaction was also reported to occur because of the transfer of di(oxyethylene) oxy units from an oligoester to the polyethylene terephthalate (PET) chain, without using a catalyst 27, 28.…”

Section: Resultsmentioning

confidence: 99%

Evaluation of compatibility and properties of biodegradable polyester blends

John

Mani

Bhattacharya

2002

J. Polym. Sci. A Polym. Chem.

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Three different biodegradable polyesters, namely, polycaprolactone (PCL), polybutylene succinate (BIONOLLE), and a copolyester of adipic acid, terephthalic acid, and 1,4‐butanediol (EASTAR) were melt‐blended using a twin‐screw extruder. The percentage composition of each of the aforementioned polymers was varied to obtain different blends, and the mechanical properties were evaluated. Selected blends showed significant improvement in tensile strength as compared with the individual polymers used to prepare the blend. The compatibility between the polymer phases was examined via Fourier transform infrared (FTIR) and nuclear magnetic resonace (NMR) spectroscopy as well as dynamic mechanical analysis. FTIR and NMR data confirmed the occurrence of hydrogen‐bonding and ester‐interchange reactions. Thermal properties and changes in crystallinity of the blends were examined with differential scanning calorimetry and X‐ray diffraction. A considerable increase in crystallinity was shown by the blend system containing BIONOLLE/PCL. The morphology of the blends was observed and correlated to the improved mechanical properties of the blend system. Results revealed an intermediate multiphase system in which a significant degree of mixing was achieved through the chemical interaction of the functional groups present, while using the twin‐screw extruder. Significant improvement in mechanical properties of some blends was observed, and information about the miscibility of these polyesters is provided. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2003–2014, 2002

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Section: Resultsmentioning

confidence: 99%

Evaluation of compatibility and properties of biodegradable polyester blends

John

Mani

Bhattacharya

2002

J. Polym. Sci. A Polym. Chem.

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“…This proposed scheme is similar to the transesterification reactions observed in polyester synthesis. 16 It is possible that upon further heating, or heating at higher temperatures, further variations may be seen. For this study, all the glasses produced at a given time point had a similar degradation rate; these rates were as low as 0.015 mg cm −2 h −1 , and compare favorably with those for calcium phosphate glasses (0.1565 to 0.0065 mg cm −2 h −1 ).…”

Section: Discussionmentioning

confidence: 99%

Synthesis, degradation, and in vitro cell responses of sodium phosphate glasses for craniofacial bone repair

Gough

Christian

Scotchford

et al. 2001

J. Biomed. Mater. Res.

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This report outlines the initial synthesis, degradation, and short-term biocompatibility of sodium phosphate glasses, for use in the drawing of fibers and manufacture of biodegradable composites. Biocompatibility studies were performed using a macrophage cell line and primary human craniofacial osteoblasts. Sodium hydrogen phosphate and sodium dihydrogen phosphate glass synthesized for less than 1 h, resulted in a higher degradation rate than glass synthesized for 3 h or more (0.015 mg cm(-2) h(-1)). Glasses with high and low ratios of hydrogen phosphate to dihydrogen phosphate had very similar degradation rates. A condensation route for the formation of the glass should give rise to varying degradation rates with varying ratios of starting materials. It is suggested that the degradation rate of the glass is independent of the concentrations of the initial reagents and that ring-opening polymerization, which reaches an equilibrium state, occurs. Biocompatibility studies suggest minimal macrophage activation (low levels of peroxide and interleukin-1beta release and rounded morphology) and high osteoblast biocompatibility. The ultimate aim of our studies is to produce a biocompatible soluble phosphate glass that can be drawn into fibers for incorporation into a polycaprolactone matrix for craniofacial bone repair. This report demonstrates the successful production of a soluble glass, which is biocompatible with regard to osteoblasts and macrophages. Recent data from our laboratory have demonstrated successful fiber drawing and production of a novel polycaprolactone.

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“…derived in the literature for the second-order reversible reaction AA + BB 2AB [6,7] and used for extracting the apparent interchange rate constant k app [9,10,13,14,18].…”

Section: General Relationsmentioning

confidence: 99%

“…To this aim, they examine whether the rate constant (extracted from the above-mentioned kinetic equation for dyads) depends on the average MW of the initial blend components [9][10][11], study the interchange kinetics in blends of model compounds [12,13] or in polymer end-capped blends [14,15], or detect the difference in composition between the copolymer and the blend as a whole [16]. However, the results are not always easy to interpret, e.g., the discussion on the main interchange mechanism in the popular blend PET/PEN still lasts [13,14,17,18].…”

Section: Introductionmentioning

confidence: 99%

End-group interchain exchange reaction in polymer blends: evolution of the block weight distribution

Kudryavtsev

Govorun

2003

E-Polymers

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Abstract:The kinetics of interchain exchange reactions proceeding via end-group mechanism in homogeneous polymer blends is studied theoretically. A set of kinetic equations describing the evolution of the block weight distribution is derived. It is demonstrated that the process may be divided into a fast and a slow stage. The fast stage is characterized by alteration in the fractions of end sequences of different type. At the same time most of the homopolymer chains transform into copolymer with block weight distribution close to the Flory distribution. In the course of the subsequent slow stage, the distribution shape is preserved, with average block lengths gradually decreasing to the values typical of the completely random copolymer. The copolymer composition is found to change mostly in the course of the fast stage of the process. The possibilities of using kinetic data for the discrimination between end-group and direct interchange mechanisms are discussed.

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A neutron scattering investigation of the transesterification of a main-chain aromatic polyester

Cited by 53 publications

References 5 publications

Evaluation of compatibility and properties of biodegradable polyester blends

Evaluation of compatibility and properties of biodegradable polyester blends

Synthesis, degradation, and in vitro cell responses of sodium phosphate glasses for craniofacial bone repair

End-group interchain exchange reaction in polymer blends: evolution of the block weight distribution

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