Effects of annealing temperature (Ta: 80-140°C) and time (ta: 3-30 h) on the crystalline phase transition in poly(lactic acid) (PLA) were studied by Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA). In the DSC curves, the sample annealed at Ta=80°C with time interval (ta: 10-30 h) demonstrates a peculiarly small exothermal peak (Texo) around 130°C, just prior to the melting point, corresponding to the disorder-to-order ('-to-) phase transition, while the sample annealed at temperature (Ta: 90-110°C) shows a double melting behavior considered as the '- phase transition. At Ta>110°C, the ′ -form of PLA was found to transform into the  one during the annealing process. The '-phase transition around 100°C (Ta: 90-110°C), determined from the two melting peaks (Tm1 and Tm2) as function of Ta at different times ta, shows a good correlation with the substantial increase in the crystallinity rate (Xc) with a maximum of 32% at Ta=120°C. Towards low temperatures, the glass modulus Eg reported by DMA thermograms, shows an important increase (30 000 MPa) at Ta=80°C for ta=3 h, due to the nucleation density extremely high in low PLA materials crystallization. After a sharp drop to 3 600 MPa at Ta=110°C, a marked improvement of Eg (15 900 MPa) is observed around Ta=120°C for all samples, regardless of time ta, temperature region where PLA is usually molded in the industrial melt processing. This interesting effect (improvement of Eg in range Ta=100-120°C) can be correlated with the grow of crystallinity in the same domain of Ta, and the '- phase transition Ta (Ta: 90-110 °C) determinate by the double Tm melting DSC peak, which is confirmed by the increase of Tg for Ta=90-110°C.

This investigation reports on the thermomechanical properties of Poly-tripropyleneglycoldiacrylate (Poly-TPGDA)/liquid crystal (LC) blends, developed via free radical polymerization processes, which are induced by Electron Beam (EB) and Ultraviolet (UV) radiation. The EB-cured Poly-TPGDA network exhibits a higher glass transition temperature (Tg), a higher tensile storage, and Young moduli than the corresponding UV-cured sample, indicating a lower elasticity and a shorter distance between the two adjacent crosslinking points. Above Tg of Poly-TPGDA/LC blends, the LC behaves as a plasticizing agent, whereas, for EB-cured networks, at temperatures below Tg, the LC shows a strong temperature dependence on the storage tensile modulus: the LC reinforces the polymer due to the presence of nano-sized phase separated glassy LC domains, confirmed by electron microscopy observations. In the case of the UV-cured TPGDA/LC system, the plasticizing effect of the LC remains dominant in both the whole composition and the temperature ranges explored. The rubber elasticity and Tg of Poly-TPGDA/LC films were investigated using mechanical measurements.

In this work we are interested with the dynamic behavior and density of PDLCs films (Polymer Dispersed Liquid Crystals).constituted of the microdroplets of nematic liquid crystal E7 dispersed in two types of polymer matrix; Tripropylene glycol diacrylate (TPGDA) or Propoxyleneglyceryl-triacrylate (GPTA). These films are prepared by polymerization induced phases separation by electron-beam (EB) or ultra-violet (UV) radiation. Films obtained are characterized by a Dynamic Mechanical Thermal Analysis. The experimental results show that GPTA films have a module of conservation higher than that of TPGDA films for the two types of irradiation. Density of these films with various thicknesses is given with and without liquid crystal for to see the effect of this last on the properties of the TPGDA/E7 and GPTA/E7 systems. The presence of microdroplets of liquid crystal E7 in the matrix TPGDA or GPTA affect the density of systems studied who is weaker for the films with matrix TPGDA; this can be connected with the nature of the monomers GPTA three-functionals, what carries with films more dense.

Effects of annealing temperature (Ta: 80-140°C) and time (ta: 3-30 h) on the crystalline phase transition in poly(lactic acid) (PLA) were studied by Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA). In the DSC curves, the sample annealed at Ta=80°C with time interval (ta: 10-30 h) demonstrates a peculiarly small exothermal peak (Texo) around 130°C, just prior to the melting point, corresponding to the disorder-to-order (a’-to- a) phase transition, while the sample annealed at temperature (Ta: 90-110°C) shows a double melting behavior considered as the a'- a phase transition. At Ta>110°C, the a′ -form of PLA was found to transform into the a one during the annealing process. The a’- a phase transition around 100°C (Ta: 90-110°C), determined from the two melting peaks (Tm1 and Tm2) as function of Ta at different times ta, shows a good correlation with the substantial increase in the crystallinity rate (Xc) with a maximum of 32% at Ta=120°C. Towards low temperatures, the glass modulus Eg reported by DMA thermograms, shows an important increase (~30 000 MPa) at Ta=80°C for ta=3 h, due to the nucleation density extremely high in low PLA materials crystallization. After a sharp drop to 3 600 MPa at Ta=110°C, a marked improvement of Eg (15 900 MPa) is observed around Ta=120°C for all samples, regardless of time ta, temperature region where PLA is usually molded in the industrial melt processing. This interesting effect (improvement of Eg in range Ta=100-120°C) can be correlated with the grow of crystallinity in the same domain of Ta, and the a’- a phase transition Ta (Ta: 90-110 °C) determinate by the double Tm melting DSC peak, which is confirmed by the increase of Tg for Ta=90-110°C.

Polymer Dispersed Liquid Crystals (PDLC) were elaborated by polymerization induced phase separation under ultraviolet (UV). A binary systems use in this study is composed of monomer of different molecular weights (TPGDA, PPGDA540 and PPGDA900), and 70 Wt.% of liquid crystal 5CB. The results showed a rapid decrease of the transmission of the LC droplet formation, followed by an enhancement of the transmission due to a thermal effect generated by exothermic curing, thermal diffusivity between components of the mixture monomers / LC, IR spectrum and high intensity of UV radiation emitted by LC3 lamp. PDLC films prepared exhibit different morphologies depending on the composition of the initial mixture, the UV dose, the molecular weight of the monomer and the nature of a LC. To quantify the effect of the molecular weight of the monomer on the kinetics of phase separation of the reactive mixtures, we realized a theoretical study that has given us a good accord with experiment.