M. J. M. Abadie

Thermoplastic biodegradable elastomers based on ε-caprolactone and l-lactide block co-polymers: A new synthetic approach

Although biodegradable polymers have found extensive application in medical devices, there are very few commercially available elastomeric biodegradable polymers. In this work, starting with the well-known monomers L-lactide and ε-caprolactone, we developed elastomers using a multiblock co-polymer approach. This ensures that the degradation products of such elastomers are also acceptable from a cytotoxicity standpoint. A series of polymers with various structures was synthesized utilizing a design of experiment approach. The basic structure is that of a diblock, with each block being modified by the addition of co-monomer. The synthesized polymers exhibited a range of mechanical properties from a typical thermoplastic polymer to that approaching a good thermoplastic elastomer. 13C nuclear magnetic resonance analysis, size exclusion chromatography and differential scanning calorimetry measurements have been utilized to relate the observed range of mechanical properties to the structure. In addition, the elastomeric nature has been established with the use of creep and recovery measurements. Such elastomers may find a variety of biomedical applications, ranging from stent coatings to atrial septal defect occluders.

Triblock copolymers of ε-caprolactone, trimethylene carbonate, and L-lactide: Effects of using random copolymer as hard-block

A series of triblock copolymers comprising end block of PLLA modified with PCL, and random copolymer of PCL and PTMC as soft segment were synthesized. DSC data show that PCL disrupted the crystallinity of PLLA, making the hard block to be completely amorphous when the PCL content is 50%. Correspondingly, the addition of PCL into PLLA block enhances the elongation of the triblock considerably. With regards to the elasticity, however, creep test results show that adding PCL to PLLA block seems to reduce the equilibrium recovery, while cyclic test results shows that the instantaneous recovery increased significantly with more PCL inside PLLA block. It was also observed that the degradation rate of triblock with added PCL inside the PLLA was slower compared to triblock with pure PLLA hard block. Compared to biodegradable polyurethane, these polymers are expected to yield less harmful degradation products, and offer more variables for the manipulation of properties. These polymers are also processable from the melt at temperatures exceeding about 130 °C. We expect to use these polymers in a variety of applications, including stent coatings, fully-degradable stents and atrial septal defect occluders.

Characterization and degradation of elastomeric four-armed star copolymers based on caprolactone and L-lactide.

Although biodegradable polymers have found extensive applications in medical areas, there are limited reports that show elastomeric behavior. In this work, a biodegradable, elastomeric polymer is demonstrated from a four-armed star copolymer. With a fixed middle core composition, comprising caprolactone (CL) and L-lactide (LA), an elastomer is obtained by increasing the polylactide (PLA) end block lengths to obtain sufficient end block crystallinity. This increase suppressed the middle cores crystallinity yet ensured cocrystallization of the PLA ends of individual star copolymer chains to form a three-dimensional network via physical crosslinking. Cyclic and creep test of the star copolymers showed that at least 75% of recovery was achieved. Degradation study of the copolymer showed that degradation first occurred in the caprolactone-co-lactide (CLLA) core, followed by degradation in the PLA ends. Chain scission in the middle core resulted in immediate formation of CL crystals within the core and increased crystallinity over time, in both CLLA core and PLA ends.

Synthesis, characterization and photopolymerization of vinyl ether and acrylate functionalized hybrid oligo-caprolactone

Linear vinyl ether-(oligo-caprolactone)-acrylate (VPCLA), combining fast free radical and complete cationic photopolymerizable groups, was synthesized, functionalized, and photopolymerized to produce polycaprolactone (PCL) network. Fourier Transform Infrared (FTIR) spectra confirmed that the C = C peaks from both vinyl ether and acrylate end groups were consumed after photopolymerization. Kinetics parameters obtained from differential scanning photo-calorimetry (DPC) analysis showed that photopolymerization of VPCLA at early stage was accelerated as the time needed to reach peak maximum was shortened, and the induction time was significantly shortened compared to monofunctional vinyl ether-(oligo-caprolactone) (VPCL). The activation energy (Ea) was calculated to be 14xa0kJ/mol, assuming second-order autocatalytic model was followed. Rate of polymerization of the hybrid oligomers was doubled in dual photoinitiators system, which contained both cationic and radical photoinitiators. Furthermore, the conversion was greatly improved at the presence of divinyl ether/hydroxybutyl vinyl ether in 1:1 ratio.

Preparation and Characterization of Sulfonated Polyphenylquinoxalines

Poly(phenylquinoxaline)s.(PPQs) are a family of aromatic condensation polymers known for their outstanding thermal and chemical stability. The pendant phenyl groups and chains isomerism improve the solubility and processing characteristics of these polymers. PPQs have also been shown to possess excellent thermo-oxidative stability and thermohydrolytic stability. This stability makes these polymers candidates for development as proton exchange membranes (PEMs) to be used in fuel cells. In addition to thermohydrolytic stability, PEMs require high protonic conductivity and, in order to achieve this they also require high water uptake. Aromatic condensation polymers do not possess these properties, but ionomers derived from them may. The usual method to derivatiziting these polymers is through sulfonation. In the frames of the present investigation we have carried out sulfonation of two PPQs using an H2SO 4—oleum mixture (4 : 1) as sulfonating agent at 125 3C. As a quinoxaline ring is readily formed in acidic medium synthesis of sulfonated PPQs (SPPQs) was also carried out directly from monomers using an H 2SO4—oleum mixture as solvent, catalyst and as sulfonating agent. Depending on the conditions of the reaction (temperature, duration, and the ratio of components in a sulfonating mixture) the polymers containing 0.2—6.7% S were prepared. SPPQs are soluble in polar organic solvents1 from the solutions of SPPQs high strength films (3 = 80—100 MPa) were cast. On the basis of sulfonated PPQs new cation-exchange membranes were prepared and investigated. Among the cation-exchange membranes developed those of the greatest interest are proton-exchanging membranes for fuel cells. Proton conductivity of the membranes prepared strongly depends on relative humidity and comparable with the conductivity of Nafion 117.

Polyethylene Terephthalate Chemical Recycling in the Melted State

In this work the results of research on polyethylene terephthalate depolymerization by the chemical recycling method in the fused state with use of alkalis are submitted. The potential of terephthalic acid and ethylene glycol reception from polymer with addition of alkalis in the melt is shown. It is established that calcium hydroxide is the optimal reagent for performing the depolymerization reaction. This method of chemical recycling does not have the demands of high temperature and pressure, it is realized in a short time and it results in products with the high cleanliness.

Auto-Reparation of Polyimide Film Coatings for Aerospace Applications Challenges & Perspectives

© 2012 Abadie et al., licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Auto-Reparation of Polyimide Film Coatings for Aerospace Applications Challenges & Perspectives

Triblock copolymers of ε-caprolactone, L-lactide, and trimethylene carbonate: Biodegradability and elastomeric behavior†

For the triblock copolymer of ε-caprolactone, trimethylene carbonate, and L-lactide, where L-lactide blocks form the two ends, there is a range of compositions over which elastomeric behavior is obtained. Within this composition range, these polymers show good creep and recovery at ambient temperature, and exhibit high elongations to break. Additionally, we demonstrate that the recovery is independent of stress and strain for the elastomer compositions. The range of compositions that yield elastomeric character is rationalized based on the structure; specifically, there must be a minimum crystallinity of the end blocks and no crystallinity in the midblock, in addition to molar mass requirements. These polymers degrade by simple hydrolysis, and the rate of degradation is potentially programmable by manipulation of the molar ratio of hard segment to soft segment. Compared to biodegradable polyurethane, these polymers are expected to yield less harmful degradation products, and offer more variables for manipulation of properties. These polymers are also processable from the melt at temperatures exceeding about 130 °C. We expect to use these polymers in a variety of applications, including stent coatings, fully-degradable stents, and atrial septal defect occluders.

Effect of the structure of the biodegradable triblock polymer polylactide-block-(polycaprolactone-stat-polylactide)-block-polylactide on its mechanical properties

The effect of the structure of the triblock biodegradable polymer synthesized from ɛ-caprolactone and L-lactide via coordination ring-opening polymerization on its mechanical properties is studied. Effects of the structure of the triblock polymer on its relative elongation at break, elastic modulus, and shape recovery after unloading are estimated by the modeling method. It is shown that the properties of the polymer in relation to its structure can be predicted. The structure-dependent characteristics of the polymers are in following ranges: relative elongation at break, 7–1500%; elastic modulus, 1–330 MPa; and shape recovery, 0–95%. The modeling data are confirmed by the back synthesis of the polymers with optimized desired characteristics.

UV curing kinetic of high performance epoxy resin for Roll-to-Roll UV embossing

In present work curing kinetics of UV-initiated cationic photo-polymerization of EPICLON series epoxy resin HP-820 and key cure process parameters, such as the extent of cross-linking and conversion, polymerization rate and the order of reactions have been studied by Photo-Differential Scanning Calorimetry (DPC). Different kinetics analysis results, including enthalpy of the reaction, induction time, peak maximum, percentage conversion were obtained for studied epoxy system at different isothermal temperatures (30–70°C), allowing calculating activation energy. Two kinetic parameters - coefficient rate (k) and the order of the initiating reaction (m) were determined, using an autocatalytic kinetics model.