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The gelation of syndiotactic polystyrene (sPS) in THF in the presence of high molecular weight PEGDME was investigated in detail using contrast-matching SANS complemented by in situ FTIR. Using the contrast-matching method, the scattering contribution of each of the two polymers in the common solution in THF at high temperature (110 °C), in the single-coil conformational state and in the gelation state of sPS (below 40 °C and down to 10 °C) was observed, and the structural characterization of the polymer coils and the junction structures of the gel was obtained. The local scale conformation of the two types of polymer molecules in the different regimes was additionally monitored by FTIR. The gelation and melting temperatures were determined by DSC. sPS changes from the amorphous coil to the helical TTGG conformation when the gelation temperature is passed, forming fibrillar morphologies with a local 2D aspect due to cooperative interactions with the solvent molecules. These are the junction structures of the large-scale network morphology of the gel. The high molecular weight PEGDME transitions from the amorphous coil to an elongated amorphous conformation and incorporates into the fibrillar morphology together with the sPS during the gelation process. High M W PEGDME alone in THF forms a "house of cards" gel consisting of stacked lamellar structures on a smaller length scale, as shown by the scattering data. Thus, in the presence of sPS, smaller and softer structures appear as a result of a cooperative gelation process controlled by sPS. Incorporation of high M W PEGDME into these aggregates leads to polymer nanocomposites that can render the sPS hydrophilic, a topic that should be the focus of future structural and morphological studies. [Display omitted] • Simultaneous SANS and FTIR provides full structural characterization of polymers. • PEGDME forms a "house-of-cards" gel morphology in THF. • Common gelation of PEGDME and sPS in THF yields a fibrillar gel. • sPS adopts a TTGG δ-form conformation without folding in fibrillar gel junctions. • PEGDME adopts an amorphous elongated conformation in fibrillar gel junctions. [ABSTRACT FROM AUTHOR]

Syndiotactic polystyrene (sPS) forms the monoclinic δ clathrate cocrystal with n-alkyl carboxylic acid (nCA). The sPS/nCA cocrystal is available not only by using the conventional guest exchange procedure but also by casting a chloroform (CHCl3) solution containing two solutes (sPS and nCA). When nCAs with carbon number of 3 to 6 are introduced into the sPS cocrystal, an appreciable amount of monomers are generated. In order to clarify how the monomeric state of the nCAs are generated by the solution casting method, the structural changes during the formation of sPS/n-hexanoic acid (nHA) cocrystal were followed by means of ATR FTIR spectroscopy. The conditions of the host sPS, the guest nHA and the solvent CHCl3 were monitored, leading the following mechanism. The sPS/nHA cocrystallization was initiated with the conformational ordering of sPS chains; the (T2G2)2 helices appeared from the solution, which was accompanied with the formation of sPS cocrystal containing CHCl3 molecules as guests. The initial guest CHCl3 molecules were gradually substituted with nHA molecules, yielding the monomeric state of nHA in the cavies of the sPS cocrystal lattice. [ABSTRACT FROM AUTHOR]

Syndiotactic polystyrene (sPS) is a crystalline polymer which has a unique property; it is able to form cocrystals with a wide range of chemical compounds, in which the guest molecules are confined in the vacancies of the host sPS crystalline region. Recently, it has been found that even polyethylene glycol oligomers with a molecular weight of more than several hundreds can be introduced into the sPS crystalline region. It is quite important to know how such a long-chain molecule is stored in the host sPS lattice. To tackle this issue, a new simultaneous measurement method combing small-angle neutron scattering and Fourier transform infrared spectroscopy (SANS/FTIR), which has been recently developed by the authors, was applied to an sPS cocrystal with polyethylene glycol dimethyl ether with a molecular weight of 500 (PEGDME500). The temperature-dependent changes of the SANS profile and FTIR spectrum were followed from room temperature up to 413 K for a one-dimensionally oriented SANS/PEGDME500 cocrystal sample. The intensity of the reflections due to the stacking of crystalline lamellae showed a significant temperature dependence. The two-dimensional pattern in the high Q region of SANS also changed depending on temperature. The combined information obtained by SANS and FTIR suggested that PEGDME500 molecules are distributed in both the crystalline and amorphous regions in the low-temperature region close to room temperature, but they are predominantly included in the amorphous region in the high-temperature region. It was also suggested by the two-dimensional SANS profile that PEGDME500 molecules in the crystalline region have an elongated structure along the thickness direction of the crystalline lamellae. [ABSTRACT FROM AUTHOR]

One of the important characteristics of syndiotactic polystyrene (sPS) is that it forms cocrystals with a variety of chemical compounds. The guest exchange procedure is an effective method to introduce diverse chemical compounds into the crystalline region of sPS cocrystals; it enables sPS to form cocrystals even with chemical compounds that are difficult to incorporate into the crystalline region by usual crystallization. The original guest in the sPS cocrystal is replaced by another chemical when exposed to a vapor, a liquid or a solution of the new guest. In order to study the characteristics of the guest exchange process initiated by exposure to a liquid, simultaneous time resolved SAXS and WAXS measurements were carried out to follow the structure changes during the guest exchange process. A series of aromatic compounds, benzene, toluene, xylene ( o- and p-isomers) and mesitylene were employed as new guests. The simultaneous measurements enabled gathering information concerning both the higher order structure and the cocrystal structure. The exchange from the old guest to the new guest was also followed by FTIR spectroscopy. It is clarified that not only the size of the new guest molecules but also the molecular shape has a significant influence on the guest exchange behavior. It is also suggested that on the liquid-phase guest exchange an expansion of the lamellar period somewhat precedes the guest exchange in the crystalline lamellae. [ABSTRACT FROM AUTHOR]

Syndiotactic polystyrene (sPS) forms cocrystals with a variety of chemical compounds. The guest molecules can be easily replaced with other kinds of molecules under certain conditions. The guest-exchange process, on exposure to liquid triethylene glycol dimethyl ether (TEGDME), is followed by time-resolved simultaneous small-angle and wide-angle X-ray scattering to clarify the structure changes in molecular-level and higher-order structures. It is clarified that the exchange from the original guest chloroform to the new guest TEGDME takes place mainly after a certain incubation time, in parallel with the expansion of the lamellar period. The occurrence of the ϵ cocrystal during this process and the influence of the amount of chloroform on the incubation time are also studied. [ABSTRACT FROM AUTHOR]

Abstract: In-situ time-resolved small angle neutron scattering is applied to the guest exchange phenomenon in the co-crystals of syndiotactic polystyrene for the first time, exploiting the significant difference in coherent scattering length between two isotopologues, fully protonated and deuterated compounds, employed as originally-occupying and subsequently-occupying guests. The vapor-induced guest exchange process between protonated toluene and deuterated one is followed by monitoring the reflection due to crystalline lamellae, which confirms that the exchange of small guest molecules like toluene proceeds smoothly in the crystalline region. In such a case, the rate of exchange is much higher than the rate of crystalline complex formation from the amorphous state induced by exposure to a vapor of guest. [Copyright &y& Elsevier]

Abstract: Syndiotactic polystyrene (sPS) forms co-crystal structures with a variety of chemical compounds. The guest exchange procedure is an effective way to prepare sPS co-crystals. The substitution is caused by exposing an sPS co-crystal film to a vapor, a liquid or a solution of the new guest molecule. In particular, the addition of an additive, such as chloroform, to the liquid of new guest molecule promotes the guest exchange process and makes bulky molecules easily incorporated into the crystalline region of sPS co-crystals. In order to obtain further information about the influence of additive as accelerant, the sorption and desorption processes of new and old guests during the guest exchange of sPS/chloroform (CHCl3) co-crystal film were followed with ATR FTIR spectroscopy. A series of n-alkanes from n-hexane to n-decane and deuterated chloroform (CDCl3) were employed as new guests and an accelerant additive. The apparent diffusion coefficients of the new and old guests were evaluated from the intensity changes of their IR bands. It has been shown that the addition of CDCl3 promotes the guest exchange between the original guest (CHCl3) and n-alkanes significantly and this effect becomes more pronounced as n-alkane chain-length increases. The diffusion of n-alkanes in atactic polystyrene was also studied for comparison, which suggested that the additive plays an important role at the stage of n-alkane uptake from the amorphous region to the crystallites. [Copyright &y& Elsevier]

Structure and dynamics of semicrystalline polymer filmscomposedof syndiotactic polystyrene (sPS) and 2-butanone were examined throughX-ray diffraction, polarized FTIR, and dielectric relaxation measurements.The X-ray and FTIR measurements revealed its crystal structure tobe ?-clathrate containing 2-butanone molecules inside. The carbonylgroup of 2-butanone in the crystal was found to orient preferentiallyparallel to the ac plane of the crystal through the polarized ATRFTIR measurements. Dielectric measurements were also conducted onthese film samples to see only the relaxation dynamics of 2-butanonethanks to the high dielectric intensity of 2-butanone compared tosPS. Two relaxation modes denoted by slow and fast modes appeared.The former was assigned to the motion of 2-butanone molecules entrappedin the cavities of the crystalline (?-form) and the latter tothose in the amorphous region. We focused on the slow mode in orderto elucidate the specific dynamics of the guest molecule confinedin the crystalline region. The relaxation time of the slow mode wasabout 4 orders of magnitude longer than that of liquid 2-butanone.This suggests that the dynamics of guest molecules is highly restricteddue to the high barrier to conformational and/or orientational changeof the guest molecule in the cavity of ?-crystal. Furthermore,the dielectric intensity ?? of the slow mode was muchsmaller than the one calculated from that of bulk liquid 2-butanoneand the guest concentration in the crystalline region (the intensitywas only 10% of the estimated value from the bulk liquid data). Thisresult also indicates that the free rotational motion of 2-butanonemolecules is restricted inside the crystal. This will be consistentlyrelated to the weak uniplanar orientation of the carbonyl group of2-butanone parallel to the acplane revealed by theX-ray and polarized ATR FTIR measurements. [ABSTRACT FROM AUTHOR]

Solid-state complexation of syndiotactic polystyrene (sPS) with three crown ether compounds, 1,4,7,10-tetraoxacyclododecane (12-crown-4, 12c4), 1, 4, 7, 10, 13-pentaoxacyclopentadecane (15-crown-5, 15c5), and 1, 4, 7, 10, 13, 16-hexaoxacyclooctadecane (18-crown-6, 18c6) took place when a film of sPS/chloroform clathrate was subjected to a guest exchange procedure assisted by a plasticizing agent. The new guest molecules were incorporated into the crystalline region of the sPS film, without causing a large conformational change of the host sPS helices. X-ray diffraction and thermogravimetric measurements showed that sPS forms co-crystalline structures with 12c4 and 15c5 presented four guest molecules per unit cell, whereas little information about the lattice dimension was obtained for sPS/18c6 because no X-ray reflections appeared in the low-angle region. IR spectroscopic and X-ray diffraction investigation suggested that the (010) uniplanar orientation of the starting sPS/chloroform clathrate was preserved during the course of guest exchange. The comparison of IR spectra between a crown ether in the liquid and crystalline states and its corresponding sPS complex showed that the crown ether incorporated into the host sPS lattice was in a conformational state similar to its liquid state, which was a mixture of two or more different conformers. It was suggested from IR and Raman spectral data that sPS/12c4 complex contained a high percentage of the Ci type conformer found in crystalline 12c4. It was inferred that the larger the molecular ring, the higher its flexibility, which leads to the lower conformational correlation of crown ether between the crystalline state and the sPS complex. [ABSTRACT FROM AUTHOR]

Guest exchange and desorption processes in syndiotactic polystyrene(sPS)-solvent complex systems (δ form) were studied by means of ATR-FTIR spectroscopy. The intensities of the bands sensitive to the amount of guest molecules and the conformational order of sPS were followed to clarify the mechanism on the guest exchange. Rapid exchange of the guest molecules was observed on the exposure of the δ form sample to toluene and chloroform vapors. The desorption of guest molecules occurs in two stages, which correspond to the rapid desorption mainly from the amorphous region and the slow desorption mainly from the crystalline region, respectively. The diffusion coefficients of the desorbate molecules were evaluated. The time dependence of the intensities of the sPS bands showed that the conformational regularity of sPS changed during the guest exchange process, and the behavior depended on the combination of sorbate and desorbate. [Copyright &y& Elsevier]

Syndiotactic polystyrene (sPS) forms cocrystals with a wide range of chemical species from low‐mass molecules to polymeric compounds, such as polyethylene glycols. Although the sPS lattice has been confirmed to accept linear compounds, such as n‐alkanes and n‐fatty acids, branched molecules have not been regarded as guests until now. To investigate whether sPS can adopt branched molecules as guests, cocrystallization using three types of monoacid triacylglycerols (TAGs) with relatively short acyl chains, tricaprin, trilaurin, and trimyristin has been attempted. Moreover, the sPS films subjected to the guest exchange procedure have been investigated via X‐ray diffraction, Fourier transform infrared spectroscopy, and simultaneous small‐ and wide‐angle neutron scattering. The results showed that sPS forms the monoclinic δ clathrate cocrystal with all the three TAGs. [ABSTRACT FROM AUTHOR]

Rotational dynamics was examined in detail for four polar aromatic molecules, benzonitrile (BN), p -methylbenzonitrile ( p -MBN), o -methylbenzonitrile ( o -MBN), and m -methylbenzonitrile ( m -MBN), accommodated in a nano-cavity regularly arranged inside the crystalline region (δ-form) of syndiotactic polystyrene (sPS) by means of dielectric relaxation measurements. Except for m -MBN, for which the co-crystalline structure was monoclinic δ-intercalate and no dielectric relaxation process arising from the crystalline region appeared, other three polar guests in the monoclinic δ-clathrate form exhibited the specific dielectric relaxation process. The relaxation times of o -MBN, BN, and p -MBN at room temperature were ranged from 10 −7 s to 10 −1 s, and in the order of o -MBN < BN < p -MBN. From the analysis of dielectric intensity data as functions of temperature, new insights about the stable and quasi-stable states of the guest molecules inside the cavity were obtained based on the two site model. [ABSTRACT FROM AUTHOR]