| Summary: | 碩士 === 國立成功大學 === 材料科學及工程學系碩博士班 === 98 === The crystallization behavior of poly(4-methylene-1-pentene) (P4MP) in the dilute p-xylene solution was studied via X-ray diffraction and transmission electron microscopy (TEM) in this research. In the range of temperature from 60℃ to 75℃, the residual Form I nuclei were able to initiate the growth of square single crystal in the 0.04% p-xylene solution. Nevertheless, as being quenched by liquid nitrogen, Form I crystal was recognized to develop within the mesophase network, instead from the nuclei. Thus it is known that as the diffusion of molecules in the dilute solution becomes a server issue upon quenching, crystallization from independent nuclei might not be preferred. Instead, crystal growth via the reorganization of mesophase can become a dominative way since much less molecular transportation is required.
Around 45℃, the Form Ⅲ square single crystals were able to grow via homogeneous nucleation process, and lead to the consumption of mesophase network. This means the mesophase can only selectively help the growth of Form I crystal. The revealed crystal growth kinetics suggests that the Form Ⅲ crystals are more stable than the state of Form I at this temperature range. The Form Ⅲ crystal can dissolve into mesophase as being heated over 85℃. In the bulk state, it is known that the Form Ⅲ crystals can only transform to Form I through solid-solid transition during heating.
Upon quenching, an unknown crystalline phase can be found except for the Form I crystals. This unknown crystalline form can transfer to Form I at 55℃ with the presence of the Form I nuclei. Since in the bulk state, only Form I crystalline form can be found, the growth of these ordered forms is clearly attributed to the presence of solvent environment. Since the solvent environment mainly affects the interfacial energy of crystals and preferred helical conformation of dissolved molecular chains, this research might reveal the importance of these two influential factors for possible crystallization routes.
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