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Poly(lactic acid) films consisting of a 0 -forms were prepared and uniaxially drawn. The effects of the draw rate at temperatures above the glass transition temperature on chain conformation, degree of crystallinity, and crystalline phase transformation were investigated by a combination of vibrational spectroscopy (infrared and Raman), differential scanning calorimetry, and wide-angle X-ray diffraction (WAXD). It was established that the a 0 -crystal's phase of poly(lactic acid) films does not transform into either an a or b crystals on uniaxial drawing at a fixed draw ratio of 4. However, the degree of crystallinity was significantly increased on deformation. The structural change as a function of deformation also promotes an increase in the strain-induced enthalpic relaxation endothermic peak appearing near the glass transition region. While the overall changes in physical properties can be attributed to the changes in the degree of crystallinity as a function of strain rate, polarized Raman spectra, and WAXD clearly illustrated changes and the differences in the amorphous and crystalline orientation as a function of processing conditions.

Based on a series of well-defined oligomers of lactic acid with different end-groups, calorimetric measurements and vibrational spectroscopic studies have been carried out to examine chain conformation and chain packing. These studies yielded data that are directly related to the models used for conformational analysis of both crystalline and amorphous PLA chains. The previously proposed rotational isomeric model dominated by the trans−gauche′−trans (tg′t) sequences has been confirmed. The linear relationship between enthalpy of fusion and reciprocal of lamellar thickness for chain-extended crystals was used to calculate the equilibrium enthalpy of melting of the α crystalline form of PLA and the value was found to be in close agreement with the previously proposed value of 93 J/g reported by Fischer. Using the same technique, the enthalpy of melting for the α′ phase has been determined to be 60 J/g. This confirms the value of 57 J/g reported by Kalish.

The kinetics of binary blends of poly(ethylene oxide)-block-poly(n-butyl methacrylate-random-propargyl methacrylate) (PEO-b-P(nBMA-r-PgMA)) diblock copolymer and Rhodamine B azide was investigated during a disorder-to-order transition induced by alkyne/azide click reaction. The change in the domain spacing and conversion of reactants as a function of annealing time were investigated by in situ small-angle X-ray scattering (SAXS) and infrared spectroscopy (IR), suggesting several kinetic processes with different time scales during thermal annealing. While a higher conversion can be realized by extending the annealing time, the microphase-separated morphology is independent of the annealing conditions, as long as both the reagents and final products have enough mobility.

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