Preferential Stereocomplex Crystallization in Enantiomeric Blends of Cellulose Acetate-g-Poly(lactic acid)s with Comblike Topology.
Although stereocomplex (sc) crystallization is highly effective for improving the thermal resistance of poly(lactic acid) (PLA), it is much less predominant than homocrystallization in high-molecular-weight (HMW) poly(l-lactic acid)/ poly(d-lactic acid) (PLLA/PDLA) racemic blends. In this contribution, the sc crystallization of HMW PLLA/PDLA racemic blends was facilitated by using comblike PLAs with cellulose acetate as the backbone. Competing crystallization kinetics, polymorphic crystalline structure, and structural transition of comblike PLLA/PDLA blends with a wide range of MWs were investigated and compared with the corresponding linear/comblike and linear blends. The HMW comblike blend is preferentially crystallized in sc polymorphs and exhibits a faster crystallization rate than does the corresponding linear blend. The sc crystallites are predominantly formed in nonisothermal cold crystallization and isothermal crystallization at temperatures above 120 °C for the comblike blends. Except for the facilitated sc formation in primary crystallization, synchrotron radiation WAXD analysis indicates that the presence of a comblike component also facilitates the transition or recrystallization from homocrystallite (hc) to sc crystallite upon heating. Preferential sc formation of comblike blends is probably attributable to the favorable interdigitation between enantiomeric branches and the increased mobility of polymer segments. After crystallization under the same temperature, the comblike blends, which mainly contain sc crystallites, show smaller long periods and thinner crystalline lamellae than do the corresponding PLLA with homocrystalline structures.
State Key Laboratory of Chemical Engineering, College of Chemical and Biological Engineering, Zhejiang University , 38 Zheda Road, Hangzhou 310027, China.
Jianna
J
Bao
State Key Laboratory of Chemical Engineering, College of Chemical and Biological Engineering, Zhejiang University , 38 Zheda Road, Hangzhou 310027, China.
Lili
L
Han
State Key Laboratory of Chemical Engineering, College of Chemical and Biological Engineering, Zhejiang University , 38 Zheda Road, Hangzhou 310027, China.
Guorong
G
Shan
State Key Laboratory of Chemical Engineering, College of Chemical and Biological Engineering, Zhejiang University , 38 Zheda Road, Hangzhou 310027, China.
Yongzhong
Y
Bao
State Key Laboratory of Chemical Engineering, College of Chemical and Biological Engineering, Zhejiang University , 38 Zheda Road, Hangzhou 310027, China.
Pengju
P
Pan
D002152:Calorimetry, Differential Scanning; D002482:Cellulose / Q000031:analogs & derivatives* / Q000737:chemistry; D002850:Chromatography, Gel; D003460:Crystallization; D007700:Kinetics; D019344:Lactic Acid / Q000737:chemistry*; D011091:Polyesters; D011108:Polymers / Q000737:chemistry*; D013237:Stereoisomerism
D011091:Polyesters; D011108:Polymers; D019344:Lactic Acid; C005062:acetylcellulose; C033616:poly(lactide); D002482:Cellulose