Application of the simultaneous measurement system of WAXD, SAXS and transmission FTIR spectra to the study of structural changes in the cold- and melt-crystallization processes of trans-1,4-polyisoprene

Abstract

The newly developed system of simultaneous time-dependent measurements of wide-angle X-ray diffraction, small-angle X-ray scattering and transmission-type Fourier-transform infrared spectra has been applied to study the structural changes in the melt-and cold-crystallization processes of trans-1,4-polyisoprene (TPI). For the melt-isothermal crystallization process at 40 1C, the domains of relatively higher density with approximately 220 Å radius formed at first as the intermediate state, where the chain conformation was speculated to be considerably disordered. As time passed, the correlation length n between these domains decreased until they joined together to form the stacked lamellar structure. In these lamellae, the crystal lattices of the regular a form were created. When the isothermal crystallization was investigated at 30 1C, the intermediate-phase regularization caused the a-and b-crystalline forms to mix. In the cold-crystallization process or the heating process that started from the melt-quenched glass below À100 1C, TPI was found to crystallize at first to the b-form at approximately À55 1C, which transformed to the a-form at 50 1C via the amorphous phase as observed above. Keywords: crystallization; structure evolution; trans-1,4-polyisoprene INTRODUCTIONRecently, we developed a system of the simultaneous and timeresolved measurement of wide-angle X-ray diffraction (WAXD), small-angle X-ray scattering (SAXS) and transmission-type FTIR spectra during the application of external fields such as temperature and tensile stress. [1][2][3] This system can provide information about the structural evolution process of synthetic polymers viewed from various hierarchical levels. The infrared spectral data show the regularization of the molecular chain conformation. This spectroscopic data can be combined with the WAXD data to reveal the crystalline lattice formation with the ordered or disordered packing of these chains. The SAXS data, which show the creation process of stacked lamellae, must also be discussed in relation to this molecular-level information. In previous works, we reported several case studies including the tensile-force-induced phase transition of poly(tetramethylene terephthalate), 1 high-temperature phase transition of aliphatic nylons 2 and isothermal crystallizations of poly(L-lactic acid) 1 and polyethylene. 3 In this paper, we will treat the structural evolution processes in the crystallization phenomena of trans-1,4-polyisoprene (TPI), which is well known as Gutta Percha and is one of the typically used biodegradable green polymers in various fields to produce artificial

Structural Evolution Mechanism of Crystalline Polymers in the Isothermal Melt-Crystallization Process: A Proposition Based on Simultaneous WAXD/SAXS/FTIR Measurements

“…The appearance of an intermediate phase can be detected clearly for this polymer [36,37]. As shown in Figure 7, where the temperature-dependent intensity change was plotted for the various IR bands in the continuous cooling process, the band at 1205 cm −1 appeared when the molten sample was cooled to about 45 °C.…”

“…The SAXS components corresponding to the longer correlation are hidden by the beam stopper. ( c , d ) The ξ min is converged finally with the averaged LP among the neighboring lamellae [36].…”

“…Temperature dependence of ( a ) IR spectra and ( b ) integrated intensity of the amorphous, intermediate and crystalline (α) bands of trans-1,4-polyisoprene measured in the cooling process from the melt [36]. …”

“…Time dependence of the various structural parameters collected for trans-1,4-polyisoprene in the isothermal crystallization from the melt. The intermediate phase started to appear immediately after the temperature jump and existed for a while until the crystalline α phase was created and increased its amount [36]. …”

Simultaneous small-angle neutron scattering and Fourier transform infrared spectroscopic measurements on cocrystals of syndiotactic polystyrene with polyethylene glycol dimethyl ethers

“…FTIR spectroscopy has been employed as a complementary tool to X-ray and neutron diffractometry and provides information about the concentration and conformational state of each chemical species in a measured object. Simultaneous analyses by X-ray scattering and FTIR spectroscopy have already been developed for synchrotron radiation facilities (Naylor et al, 1995;Innocenzi et al, 2007;Jaya Ratri & Tashiro, 2013). Similarly, the combination of FTIR spectroscopy with SANS would produce a fruitful methodology for such a simultaneous measurement system.…”