Integration Of Ultrafast Scanning Calorimetry And Raman Spectroscopy, And Ultrafast Scanning Calorimetric Probing Into Dynamics Of Phase Separation

Ultrafast scanning calorimetry (UFSC) has been given close attention in material science in recent years for the advantages of high heating and cooling rates that normal techniques cannot achieve. This approach can be used in researches of crystallizing polymers, liquid crystals, metal alloys, crystallization and glass transition of some other materials. And more importantly, UFSC makes it more convenient to study some metastable or intermediate states of materials.Recently, Schick and co-workers developed a non-adiabatic power compensated chip calorimetry using commercial thermal conductivity gauge, the heating, as well as cooling rates can be up to105K/s. This approach has been successfully used in researches of melting-crystallizing-remelting processes of various polymers, the volatility of ionic liquids and even silks. UFSC is getting more and more feasible and comprehensive, which makes it possible for further development and application of this technique.Based on the non-adiabatic power compensated chip calorimetry, we designed and developed a stage-type ultrafast scanning calorimetry in this work. Compared to tube-dewar type UFSC proposed by Schick et al., the sample chamber of stage-type UFSC is limited to30mm in thickness, and can be conveniently integrated with several kinds of optical characterization techniques as it has paths both for the transmission and reflection. In this work, we integrated the stage-type UFSC with confocal microscope Raman spectroscopy on-the-spot. An asynchronous way was adopted that we firstly performed heat treatments on the stage-type UFSC, and quenched the sample, then Raman spectra were collected in-situ. Besides, we have quantified the temperature increase of sample induced by Raman laser, and brought forward a working mode called Tsamp mode. We can effectively control the temperature of sample to the set point so that to prevent the affection of the heating effect by Raman laser to the state of sample.The integrated techniques were used to investigate the isothermal crystallization process of poly(ethylene terephthalate) annealing at450K. The results of Raman spectra reveal that both of the relative intensity at1092cm-1band and the width of1724cm-1band show a rapid change starts from about5s and ends at100s. It indicates that there is a fast crystallization period for this sample during annealing5s to100s, as they are linear correlated with the crystallinity of the sample. Comparing with these results, the enthalpy of fusion in the heating scans were calculated and turned out to be in great coincidence with the results of Raman spectra. The integrated techniques, as well as the results derived from them, hereby, can be concluded to be reliable.In addition, we tried to study the dynamics of phase separation in polymer blends using UFSC in this work. A binary polymer blend system PVME/PS, which shows lower critical solution temperature behavior, was taken as model system. Firstly, the state diagram of this blend system was constructed using a temperature jump methodology. It shows that the curve of critical phase separation temperature crosses over the homogenous glass transition temperature curve for compositions richer in PS than about54wt%. And then, the phase separation process at350K for the sample with30wt%in PS was followed using UFSC. The Tgs of PVME-rich phase after annealing different time were detected during heating scans. According to the Kwei fit of homogenous Tg curve, the weight fraction of PS in PVME-rich phase versus phase separation time was derived. The result shows that the system is in the stage of diffusion for annealing time less than5s, while it is in the stage of liquid flow for phase separation time during5s to900s, and in the coalescence stage after that.At last, we concluded our work, and discussed about the future work that could be done for the integration of UFSC and Raman spectroscopy and application of UFSC on the investigation of phase separation dynamics of polymer blends. We hope that our work could be considered as references for the development and applications of UFSC.