Liquid Induced Polycarbonate Crystal And Polycarbonate Gold Nanoparticles Composites

The liquid-induced crystallization behavior of bisphenol-A polycarbonate(BAPC) by carbon tetrachloride,butyl acetate,tetrahydrofuran or acetone was thoroughly investigated by differential scanning calorimetry(DSC) and the crystal structure was detected by wide angle X-ray diffraction(WAXD).The crystallization morphologies were observed by polarized optical microscopy(POM) and scanning electron microscopy(SEM).The experiment results showed that the crystallization ability can be greatly enhanced in the presence of butyl acetate,tetrahydrofuran and acetone with a rapid increase of crystallinity and crystallization process.Acetone was implemented with great efficiency as the induced crystallization agents for BAPC.After liquid-induced by acetone for 1 minute,the crystallinity already reached 17.5%,higher than the crystallinity produced by the liquid inducement by tetrahydrofuran for 1 day or butyl acetate for 4 days respectively and even higher than the crystallinity of 16.8%created by melting crystallization for 22 days.However,carbon tetrachloride exhibited no obvious ability to induce the crystallization of BAPC.On the other hand,the high temperature melting peak accompanied with low temperature melting peak was observed after the induced crystallization by the three solvents,indicating that two kinds of lamellae with different thickness was formed.And the lamella thickness created by acetone was higher than that created by butyl acetate and tetrahydrofuran. Moreover,WAXD spectra displayed that acetone could induce larger lateral size of crystal grains than that by butyl acetate and tetrahydrofuran.DSC was employed to particularly study the acetone liquid-induced crystallization behavior of BAPC.The great reduction of Tg after the absorption of acetone indicative of the improvement of the chain mobility was the confirm of the role of the organic solvent as plasticizer.During the acetone liquid-induced crystallization at 25℃,the crystallinity increased with the increase of the inducing time with a shifted to rise of crystallinity in the initial stage of the crystallization.The increasing rate of the crystallinity then slowed down and reached a steady value of 21.5%.Meanwhile,the low temperature melting peak displayed in DSC results shifted to higher temperature while the high temperature melting peak remained in original place when the inducing time increased,implying that the thickness of the thinner lamella corresponding to the low temperature melting peak continually increased from 8.6 nm to 8.9 nm while the thickness of the thicker lamella corresponding to the low temperature melting peak remained 10.0 nm.Compared with the vapor induced crystallization,the crystallinity, crystallization rate and lamellae thickness produced from liquid-induced crystallization were larger.Inducing temperature exerted a strong influence on the acetone liquid-induced crystallization of BAPC.With the higher inducing temperature,the maximum value of crystallinity enhanced,from 21.5%at 25℃to 29.6%at 45℃.Meanwhile,the average lamella thickness rose from 8.7 nm and 10.0 nm at 25℃to 9.0 nm and 10.3 nm at 45℃.On further,the period of the initial stage in which the crystallinity enjoyed a fast increasing rate turned longer at higher inducing temperature,from 50 min at 25℃to 10 h at 45℃.It was also detected that the thicker BAPC sample could promote the induced crystallization to some extent.WAXD was used to measure the crystals structure of BAPC samples by acetone liquid-crystallized in varied conditions.The results showed that the liquid-induced crystal grain size was larger than that of vapor-induced crystallization.Moreover,on the occasions when BAPC was induced crystallized at higher inducing temperature, the crystal grain size was larger as well,which implied a more orderly crystal structure.From the analysis of the various crystallinity based on the diffusion behavior of acetone,the kinetics of liquid-induced crystallization was controlled by the crystallization process while the acetone diffusion followed the CaseⅡdiffusion pattern.POM and SEM were involved to observe the acetone liquid-induced crystallization morphologies.Spherulites of 8μm in diameters were observed after the immersion in acetone for 10s and expanded to 11μm after the immersion for 40s with a denser aggregation.The observation of SEM showed that spherulite sizes increased when crystallization advanced and reached the maximum value of 18μm at 25℃.When the inducing temperature became higher,spherulites sizes also developed and arrived at 20μm at 45℃.Compared with liquid-induced crystallization,spherulites formed by vapor-induced crystallization were smaller but denser.The vacuum evaporation technique was adopted to form a coating of noble metal gold on BAPC film followed by acetone liquid-induced crystallization at 45℃.The cross-section of the samples was observed by TEM.The observation results exhibited the interesting automatic dispersion of gold clusters during the liquid-induced crystallization with the dispersion depth of 350nm of gold clusters with the size about 10～15nm after BAPC film was acetone liquid-induced crystallized at 45℃for 3 days. The gold clusters were detected to disperse more quickly in the period when the crystallinity processed a fast increasing rate.The experiment results could offer a novel technical method to prepare metal-polymer nanocomposite through induced polymer crystallization.