Structural study on the molecular conformation and orientation of large molecules stored in
the cocrystals of syndiotactic polystyrene using simultaneous SANS, WANS and polarized
FTIR measurements.
Graduate School of Science, Osaka University

Fumitoshi Kaneko

1. Introduction
Syndiotactic polystyrene (sPS) exhibits a variety of solid states. One of the important characteristics of sPS is
the formation of crystalline cocrystals, where organic compounds are stored as guests in the cavities in thecrystalline region. The guest molecule can be exchanged with other molecule; we have clarified that a variety ofcompounds including functional molecules can be incorporated into sPS lattice by using this guest exchange
phenomenon [1, 2].
material [3-5].

The sPS cocrystals seems to have a significant potential as a new kind of functional

Actually, it has been clarified from the scattering (X-ray and neutron) and FTIR experiments thatsPS forms cocrystals with polymeric materials, such as, polyethylene glycols[6,7]. Since the volume of this kindof guest molecules is much larger than the available space in a cavity of sPS cocrystals, it is inferred that such along guest molecule is accommodated in a completely different manner from the ordinary sPS cocrystal, whereone guest molecule occupies a cavity. It is highly plausible that the long molecule settles in the sPS cocrystal byusing several cavities.
The purpose of this study is to clarify the structure and orientation of such large guest molecules stored in thecocrystals of sPS. So far, we have been studying sPS cocrystals by using IR spectroscopy, X-ray scattering andalso neutron scattering [8]. Furthermore, we have recently developed a simultaneous time-resolved SANS/FTIR
measuring system [9,10], which is able to supply the information about not only higher-order structure but also
the molecular-level structure and the amount of chemical species.

To enrich structure information, we have tried

to introduce this methodology to a small- and wide-angle neutron scattering instrument, BL15 TAIKAN, and also
analyze the polarization of vibrational modes by installing a polarizer.
References [1] Y. Uda, F. Kaneko, T. Kawaguchi, Macromol. Rapid Commun. 25, 1900, 2004. [2] F. Kaneko, T.
Tsuchida, Polymer 54, 760, 2013. [3] Y. Uda, et al. Adv. Mater. 2005, 17, 1846. [4] G. Guerra et al. in
Syndiotactic polystyrene ed. J. Schellenberg, 2009 Hoboken, Wiley [5] G. Guerra et al. J. Polym. Sci. Polym. Phys.
50, 305, 2012. [6]F. Kaneko, K. Sasaki, Macromol. Rapid. Commun. 32, 998, 2011. [7] F. Kaneko, N. Seto, K.
Sasaki, S. Sakurai, Chem. Lett 43, 904, 2014. [8] F. Kaneko, A. Radulescu, K. Ute, J. Appl. Crystallogr., 47, 6-13
(2014) [9] F. Kaneko, N. Seto, S. Sato, A. Radulescu, M. M. Schiavone, J. Allgaier, K. Ute, Chem. Lett. 44,497-499 (2015). [10] F. Kaneko, N. Seto, S. Sato, A. Radulescu, M. M. Schiavone, J. Allgaier, K Ute, J. Appl.
Crystallogr. J. Appl. Cryst. 49, 1420–1427 (2016).

2. Experiment
For this study, we built an experimental setup shown in Figure 1 forsimultaneous neutron scattering and polarized FTIR measurements, as shown inFigure 1.

For polarization analyses, a remote control IR polarizer was set justafter the outlet IR beam port of a portable FTIR spectrometer (JASCO, VIR200).
The two mirrors are Al-coated quartz plates, which transmit neutron beams andreflect infrared rays. The first mirror acts as a beam mixer and the second one asa beam separator. The IR and neutron beams impinges the same position of thesample coaxially and the transmitted beams are delivered to their own detectors.
1

Figure 1: Simultaneous
SANS/WANS/ Polarized FTIR
measuring system; (1) polarizer,(2) (3) mirrors, (4) cell housingand (5) sample cell.

Fully deuterated syndiotactic polystyrene (d-sPS) was synthesized.

Uniaxially oriented amorphous d-sPS

samples, about 50 µm thick, were prepared by quenching a melt of d-sPS into an ice–water bath, drawing themelt-quenched film four times in an oil bath kept at 100˚C, and clipping well oriented portions from the drawn
film. The oriented amorphous films were exposed to a vapor of toluene to give oriented samples of d-sPS/toluene
cocrystal. The cocrystal films were soaked in a target guest molecule/deuterated chloroform mixture over a week
and then kept in a vacuum oven at 40˚C for an hour to remove excess
chloroform, giving uniaxially oriented cocrystal film samples.
Thus prepared d-sPS cocrystal film samples were subjected tosimultaneous SANS/WANS/FTIR measurements.

Temperature dependentchanges were observed in the range of 25 to 125˚C.
3. Results
Figure 2 shows an example of temperature dependent SANS and WANS
profile changes.

The fiber axis direction is set parallel to the verticaldirection, and therefore, the reflections due to lamellar stacking appear on
the meridian.

The d-sPS cocrystal includes diethylene glycol dibenzoate(DEGDBA), C6H5O(C2H4O) C6H5, as guest.

In such d-sPS cocrystals

containing protonated guests, the distribution of the guest is the principal+0.25

factor to determine the neutron scattering profile.

0.00

In the lower temperature region, the sPS cocrystal showed clear 010
reflections at around q = 0.6 Å-1 on the equator, which indicated that
DEGDBA molecules were stored in the crystalline region; the regulararranagement of DEGDBA in the lattice creates a clear scattering contrast.
However, the 010 reflections gradually waned as the temperature increased.

-0.25
-0.75

0.00

+0.75
( Å-1)

Figure 2.
Scattering profileof a uniaxially oriented film ofd-sPS / h-DEGDBA cocrystal.
LR: lamellar reflection.

Instead the lamellar reflections appeared on the meridian and increased in intensity with temperature.
These changes in the WANS and SANS regions suggest the migration of protonated guest DEGDBA
molecules from the crystalline region to the amorphous region of deuterated sPS matrix, since the migration
results in a decrease in the scattering contrast (SC) within the crystal lattice and an increase in the SC between thecrystal lattice and amorphous regions.
The polarized IR spectra obtained were consistent with this interpretation. The host d-sPS did not show any
significant spectral changes, keeping the polarization of each band, which suggests that the orientation andconformation of d-sPS remained almost unchanged during heating process. The bands due to DEGDBA did notshow significant intensity changes, which suggests that the gross amount of DEGDBA within the film sample waskept unchanged.
4. Conclusion
As described above, the present study has shown that the simultaneous SANS, WANS and FTIR
measurements are able to provide valuable information about the polymer co-crystal system. By combining thedata obtained by SANS with those obtained by WANS, the location of guest molecules can be derived with alarger certainty.

Furthermore, the polarized IR spectroscopy can add the information about the conformation andorientation of the host and guest.

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