Crystallization And Melting Of Macromolecules Studied By Fast-scan Chip-calorimeter

The fast-scan chip-calorimeter,a novel power-compensation differential scanning calorimeter,has attracted broad research attention,due to its ultra-high scanning rate,the super-high time resolution and the very-small sample size in thermal characterization.In this thesis,we systematically investigated the crystallization or melting behaviors of isotactic poly(cyclohexene carbonate)(iPCHC),Poly(lactic acid)(PLA),syndiotactic polystyrene(sPS)and solid-state bovine serum albumin(BSA)by using the commerciallized fast-scan chip-calorimeter named Flash DSC 1.In Chapter 1,we introduced basic concepts of polymer crystallization and melting,as well as the background of protein crystallization and denaturation.The corresponding characterizations of protein crystallization were summarized.In addition,the relationships between protein denaturation and unfolding were illustrated in details,as well as the mechanism of protein unfolding and the influence of external forces on it.In Chapter 2,we made a survey on the history and the future trend of both commercial and non-commercial fast-scan chip-calorimeter techniques.The advantages of Flash DSC 1 on polymer crystallization were discussed,in particular,in the accurate control of thermal history for isothermal and non-isothermal crystallization.We also introduced the polymer crystallization behavior when the nucleating agent and particle filler co-exist,the determination of multiple endothermic peaks during heating,superheating and reversible melting,and inhibition of thermal degradation by using the ultra-fast heating.In Chapter 3,we used Flash DSC 1 to investigate the isothermal crystallization kinetics of several green polymer materials.We first investigated the isothermal crystallization kinetics of iPCHC,and observed the curves of half-crystallization time versus temperature exhibiting single bell shape,not common among other polymers.We attributed this phenomenon to the rigid short chain structure.Next,we investigated the growth and nucleation kinetics of PLA,and observed PLLA/PDLA blend crystallized at an intermediate temperature.In Chapter 4,we used Flash DSC 1 to investigate the melting behavior of meltcrystallized sPS.According to the melting curves under variable heating and cooling rates,the phenomenon of double melting peaks can be explained by the melting-recrystallization process,as in the ?'-form crystals identified by X-ray diffraction.In Chapter 5,we used Flash DSC 1 to determine the crystallinity of solid-state BSA.We proved that the endothennic peak of solid-state BSA around 220? corresponds to the unfolding.We obtained the fusion enthalpy of BSA crystals,which is about 6.9 J/g.Finally,we determined the crystallinity of the semi-crystalline BSA,and the result was confirmed by the comparison between the measured heat capacity and the value calculated from the crystallinity.At the end,we summarized our conclusions and make a perpective on further applications of Flash DSC 1 in the investigations of macromolecular crystallization and melting.