Ring-opening graft polymerization (ROGP) of L-Lactide (L-LA) is a practical method of altering the physical and chemical properties of lignocellulose. Previous studies have mainly investigated cellulose and tin-based catalysts, particularly of tin(II) 2-ethylhexanoate (Sn(oct)2), at high temperatures and reported low graft efficiencies. In the present study, ROGP of L-LA was successfully achieved on xylan-type hemicelluloses in ionic liquid (IL) 1-allyl-3-methylimidazolium chloride ([Amim]Cl) using 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as an effective organic catalyst. Mild reaction condition (50 °C) was used to limit transesterification, and thus enhance the graft efficiency. The hydroxyl groups on xylan acted as initiators in the polymerization, and DBU, enhanced the nucleophilicity of the initiator and the propagating chain. Xylan-graft-poly(L-Lactide) (xylan-g-PLA) copolymer with a degree of substitution (DS) of 0.58 and a degree of polymerization (DP) of 5.51 was obtained. In addition, the structures of the xylan-g-PLA copolymers were characterized by GPC, FT-IR and NMR, confirming the success of the ROGP reaction. Thermal analysis revealed that the copolymers exhibited a single glass-transition temperature (T g), which decreased with increasing molar substitution (MS). Thus, modification resulted in the graft copolymers with thermoplastic behavior and tunable T g.

译文

L-丙交酯 (L-LA) 的开环接枝聚合 (ROGP) 是改变木质纤维素物理和化学性质的实用方法。先前的研究主要研究了纤维素和锡基催化剂,特别是2-乙基己酸锡 (II) (Sn (10月) 2),在高温下,并报告了低接枝效率。在本研究中,使用1,8-二氮杂双环 [5.4.0]undec-7-ene (DBU) 作为有效的有机催化剂。温和的反应条件 (50 ℃) 用于限制酯交换,从而提高接枝效率。木聚糖上的羟基在聚合反应中充当引发剂,而DBU,增强了引发剂和传播链的亲核性。获得了取代度 (DS) 为0.58,聚合度 (DP) 为5.51的木聚糖-接枝聚 (L-丙交酯) (木聚糖-g-PLA) 共聚物。此外,通过GPC,ft-ir和NMR表征了木聚糖-g-PLA共聚物的结构,证实了ROGP反应的成功。热分析表明,共聚物表现出单一的玻璃化转变温度 (T g),随着摩尔取代 (MS) 的增加而降低。因此,改性导致接枝共聚物具有热塑性行为和可调T g。

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