Photon Factory Activity Report 2017 #35 (2018)

BL-10C/2018G026

Effects of A Liquid-type Crystallization on Isothermal Crystallization Behaviors ofPoly(L-Lactic Acid) as Analyzed by Simultaneous Small- and Wide-Angle X-Ray
Scattering Measurements
Pham Thi Ngoc DIEP1, Masatsugu MOCHIZUKI2, Mikio DOI2, Vimal KATIYAR3, Sono
SASAKI1, Shinichi SAKURAI1*1

Department of Biobased Materials Science, Graduate School of Science and Technology, Kyoto
Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585, Japan
2
Taiyo Kagaku Co., Ltd., Mie, Japan3
Indian Institute of Technology Guwahati, India

1 Introduction
Poly(L-lactic acid) (PLLA) is a biodegradable andbiocompatible polymer which can be synthesized fromrenewable sources such as sugar, carbohydrate, etc.
However, there existing some big problems of PLLA,
which are low crystallization rate and low crystallinity. Inorder to overcome such drawbacks, nucleation agents
have been incorporated into PLLA. In this study, weadded a special liquid-type nucleation agent (organic acidmonoglyceride; OMG) into PLLA in order to improve thecrystallization abilities of PLLA. In this study, we
conducted differential scanning calorimetric (DSC)
measurements, polarizing optical microscopy (POM)
observations, and simultaneous small- and wide-angle Xray scattering (SWAXS) measurements to follow
isothermal crystallization.
2 Experiment
There are two types of neat PLLA samples such as
PLLA4032D (1.4 % D-content: D1.4) and PLLA2500HP(0.5 % D-content: D0.5) from Nature Works and PLLA
with OMG (1% addition) such as D1.4/OMG and
D0.5/OMG specimen. The non-isothermal crystallization
took place in the heating process (with rates of 2.5, 5, 7.5
and 10˚C/min) of the specimen which was cooled downfrom the molten state, while the isothermal crystallization
was induced by the T-jump from the molten state (at 200˚C) to a given crystallization temperatures (90, 110,130˚C).
The SWAXS measurements were conducted at BL-10Cof Photon Factory in High Energy Accelerator ResearchOrganization (Tsukuba, Ibaraki, Japan). The beamline
was composed of an approximate toroidal mirror,
monochromator, four-quadrant slits, and a twodimensional detector (PILATUS 300 K, DECTRIS Ltd.,
Baden, Switzerland), on which X-ray was focused. The
sample-todetector distance was 2.0 m, and the wavelengthof X-ray was 0.150 nm.
Time-resolved SWAXS
measurements wer performed upon temperature jumpfrom 200ºC to 112.3ºC (cooling rate was approximately
90ºC/min). The time-resolved SAXS measurement wasconducted with 30s step while the time-resolved WAXS
was conducted with 5s step. The revolution of crystalline
peak being ascribed to the long period of stacking of thecrystalline lamellae, was analyzed as a function of time.

Fig. 1 Change in the Lorentz-corrected 1d-SAXS
profiles (plots of q2I(q) vs. q, for thePLLA2500HP/OMG specimen.
3 Results and Discussion

Fig. 1 shows the typical changes in the Lorentzcorrected 1d-SAXS profiles (plots of q2I(q) vs. q, for
the PLLA2500HP/OMG specimen. A broad peak
finally appeared in the q-range of 0.3 ~ 0.36 nm-1.
This peak reflects the period of stacking of the lamellar
crystals (so-called long period). Therefore, the onset
time of the peak evolution can be a measure of theinduction period of crystallization. In order to evaluate
the onset time, computational peak decomposition wasperformed for the Lorentz-corrected SAXS profile.
Thus obtained integrated peak intensity (peak area)
was plotted as a function of the time elapsed, and by
extrapolation of the dependencies, the onset time wasfinally evaluated. Based on thus evaluated onset time,
it can be stated that the liquid OMG plays a role ofcrystallization agent.
* shin@kit.ac.jp