Interfacial effects on the crystallization of poly(L-lactic acid) studied by using AC nano-calorimetry
Purpose
Poly(L-lacticacid) (PLLA) is one of the most popular bioplastics nowadays. The “bio-” means that it is not only biodegradable at the ambient environment but also can be produced from the renewable biomass such as corn.There are many points that have not yet been elucidated about the physical properties of PLLA. So I am studying the crystallization of it.
Describe experiment
In order to measure the crystallization rate, a method such as differential scanning calorimetry (DSC) has been conventionally used, but with a nano-sized polymeric material the sample is too small to detect the signal. Therefore, we fabricated a prototype device that measures the total crystallization rate of macromolecules that can measure more minute signal detection. In this research, we have established measurement techniques for directly evaluating thermal properties of polymer thin films using nano calorimetry.
PLLA was prepared to be a uniform solution (2 wt%) in chloroform. One droplet of the prepared solution was dropped on a chip with a Pasteur pipette and left for 10 minutes in the room. Thereafter, it was vacuum-dried for 24 hours using a vacuum dryer.In the isothermal crystallization experiment, the temperature amplitude difference between the sample chip (chip A) and the reference chip (chip B) connected in series was observed. The temperature amplitude is inversely proportional to the heat capacity of the sample. When crystallization occurs, the thermal capacity of the sample decreases and the temperature amplitude increases, but the absolute value of the difference in temperature amplitude between chip A and chip B decreases. That is, the difference between the heat capacity of the sample and the heat capacity of the reference is reduced. Therefore, the measured value (that is, the difference in temperature amplitude between chip A and chip B) decreases with crystallization. In addition, when measuring the crystallization rate of each sample by using a block heater, the measurement time was maintained at 40 ° C. for 600 seconds and isothermal crystallization was performed. As the setting of the lock-in amplifier, the frequency of the alternating current was set to 80 Hz AC voltage to 300 mV. Points were taken at 1 second intervals and measured. The sample on the chip measured once was not discarded, melted and used for measurement again.
Result
We evaluated the cold crystallization rate of thin films of poly(L-lactic acid) by using AC nano-calorimetry under quasi-isothermal conditions. The crystallization rate was enhanced when the surface of the film was in contact with poly(ethylene glycol), while no apparent change was observed in the case of silicone oil.
Purpose
Poly(L-lacticacid) (PLLA) is one of the most popular bioplastics nowadays. The “bio-” means that it is not only biodegradable at the ambient environment but also can be produced from the renewable biomass such as corn.There are many points that have not yet been elucidated about the physical properties of PLLA. So I am studying the crystallization of it.
Describe experiment
In order to measure the crystallization rate, a method such as differential scanning calorimetry (DSC) has been conventionally used, but with a nano-sized polymeric material the sample is too small to detect the signal. Therefore, we fabricated a prototype device that measures the total crystallization rate of macromolecules that can measure more minute signal detection. In this research, we have established measurement techniques for directly evaluating thermal properties of polymer thin films using nano calorimetry.
PLLA was prepared to be a uniform solution (2 wt%) in chloroform. One droplet of the prepared solution was dropped on a chip with a Pasteur pipette and left for 10 minutes in the room. Thereafter, it was vacuum-dried for 24 hours using a vacuum dryer.In the isothermal crystallization experiment, the temperature amplitude difference between the sample chip (chip A) and the reference chip (chip B) connected in series was observed. The temperature amplitude is inversely proportional to the heat capacity of the sample. When crystallization occurs, the thermal capacity of the sample decreases and the temperature amplitude increases, but the absolute value of the difference in temperature amplitude between chip A and chip B decreases. That is, the difference between the heat capacity of the sample and the heat capacity of the reference is reduced. Therefore, the measured value (that is, the difference in temperature amplitude between chip A and chip B) decreases with crystallization. In addition, when measuring the crystallization rate of each sample by using a block heater, the measurement time was maintained at 40 ° C. for 600 seconds and isothermal crystallization was performed. As the setting of the lock-in amplifier, the frequency of the alternating current was set to 80 Hz AC voltage to 300 mV. Points were taken at 1 second intervals and measured. The sample on the chip measured once was not discarded, melted and used for measurement again.
Result
We evaluated the cold crystallization rate of thin films of poly(L-lactic acid) by using AC nano-calorimetry under quasi-isothermal conditions. The crystallization rate was enhanced when the surface of the film was in contact with poly(ethylene glycol), while no apparent change was observed in the case of silicone oil.