Photon Factory Activity Report 2014 #32 (2015) B

BL-6A&BL-10C/2014G570

SWAX measurement on co-crystallization of syndiotactic polystyrene
with linear polymers
Fumitoshi Kaneko1,* and Shuma Sato1
1Graduate School of Science, Osaka University, Toyonaka 560-0043, Japan
1 Introduction
Syndiotactic Polystyrene (sPS) occupies a peculiar
position among crystalline synthetic polymers. One ofthe important properties concerning the solid states of sPS
is the variety of crystalline states. It shows several
polymorphs depending on the crystallization conditions
and subsequent treatments. Also, it forms some cocrystal states with a variety of chemical compounds. The
co-crystal states of sPS are classified into at least fourgroups, depending on the crystal system and the size andshape of spaces that guest molecules occupy. In these cocrystal states, guest molecules are included in cavities
formed by sPS helices of TTGG conformation. The
polymer-crystalline-region-based complex found in sPS isunprecedented in synthetic polymers with respect toconsiderable variety of guest molecules. The of sPS cocrystal states as new kinds of functional polymer
materials attracts attention, and many studies are actively
being carried out.
Recently we have clarified that cyclic and linear
molecules consisting of
ethylene oxide (CH2CH2O)
repeat units can be easily incorporated into the crystalline
region of sPS co-crystals through guest exchange
procedure. Chemical compounds with a wide variety ofmolecular weights, from 176 (12-crown-4) to 2000 (PEG2000), have been confirmed to form co-crystal with sPS.
We have expected that other polymeric compounds
would also exhibit complexation with sPS, if thefollowing prerequisites are satisfied; (1) a strong affinity
to the cavity in host sPS crystalline region and (2) asuitable flexibility of the main chain. According to thisexpectation, we have studied the complexation ofpolypropylene glycol (PPG) [(-CH2CH(CH3)O-)n]oligomers with sPS in this study.
2 ExperimentsPS was provided by Idemitsu Kosan Corp. The
following PPG related compounds were employed as newguests: dipropylene glycol dimethyl ether (DPGDME),
Tripropylene glycol (TPG), and PPGs with mw 400 and1000 (PPG400 and PPG1000).
Diethylene glycol
dimethyl ether (DEGDME) was also used for comparison.
In order to measure clear lamellar reflections in a welldefined area, 4-5 times uniaxially drawn sPS films about
50 µm thick were prepared. Starting samples ofsPS/chloroform cocrystal were prepared by exposing thesPS films to chloroform vapor. Time resolved
simultaneous SAXS and WAXS measurements werecarried out at BL-6A and BL-10C. The guest exchange
process was initiated by injecting a liquid of new guest(or a mixture with an additive) into a glass capillary
containing several pieces of sPS/chloroform co-crystalfilm.

Int.
(a.u.)

Time (min)Fig. 1. Intensity changes in 010 (blue) and 2 10 (red)reflections during the guest exchange process fromchloroform to DPGDME.

€Fig. 2. SAXS profilechanges during the guest
exchange process of sPS
co-crystals. The two spots
are due to the lamellar
stacking of sPS cocrystals.
3. Results and Discussion
On exposure of sPS/chloroform films to a neat liquidof DPGDME, marked changes appeared both in theSAXS and WAXS images. Fig. 1 shows the intensitychanges in the 010 and 2 10 reflections on the equator inthe WAXS image, which kept on changing over 2 hours.
In the meantime, the lamellar reflections in the SAXS
images increased significantly in intensity and shifted to alower angle. € These changes indicate that DPGDME isalso able to form a co-crystal structure with sPS.
Compared with the guest exchange process of DEGDME,
in which major SAXS and WAXS changes completed inabout 10 min, DPGDME spends a considerable amountof time intruding into the sPS co-crystal lattice, which ispresumably due to the steric hindrance of side methylgroups.
We also investigated the changes in SAXS andWAXS profiles of sPS co-crystal films after the guest
exchange treatment for about a week, and observed
similar changes, which strongly suggests the possibility
that sPS forms co-crystals with high-molecular PPGs.
* toshi@chem.sci.osaka-u.ac.jp