Wei Liqing, McDonald Armando G, Stark Nicole M
Renewable Materials Program, Department of Forest, Rangeland and Fire Sciences, University of Idaho , Moscow, Idaho 83844-1132, United States.
Biomacromolecules. 2015 Mar 9;16(3):1040-9. doi: 10.1021/acs.biomac.5b00049. Epub 2015 Feb 18.
Polyhydroxybutyrate (PHB) was grafted onto cellulose fiber by dicumyl peroxide (DCP) radical initiation via in situ reactive extrusion. The yield of the grafted (cellulose-g-PHB) copolymer was recorded and grafting efficiency was found to be dependent on the reaction time and DCP concentration. The grafting mechanism was investigated by electron spin resonance (ESR) analysis and showed the presence of radicals produced by DCP radical initiation. The grafted copolymer structure was determined by nuclear magnetic resonance (NMR) spectroscopy. Scanning electronic microscopy (SEM) showed that the cellulose-g-PHB copolymer formed a continuous phase between the surfaces of cellulose and PHB as compared to cellulose-PHB blends. The relative crystallinity of cellulose and PHB were quantified from Fourier transform infrared (FTIR) spectra and X-ray diffraction (XRD) results, while the absolute degree of crystallinity was evaluated by differential scanning calorimetry (DSC). The reduction of crystallinity indicated the grafting reaction occurred not just in the amorphous region but also slightly in crystalline regions of both cellulose and PHB. The smaller crystal sizes suggested the brittleness of PHB was decreased. Thermogravimetric analysis (TGA) showed that the grafted copolymer was stabilized relative to PHB. By varying the reaction parameters the compositions (%PHB and %cellulose) of resultant cellulose-g-PHB copolymer are expected to be manipulated to obtain tunable properties.
通过过氧化二异丙苯（DCP）自由基引发，采用原位反应挤出法将聚羟基丁酸酯（PHB）接枝到纤维素纤维上。记录了接枝共聚物（纤维素-g-PHB）的产率，发现接枝效率取决于反应时间和DCP浓度。通过电子自旋共振（ESR）分析研究了接枝机理，结果表明存在由DCP自由基引发产生的自由基。通过核磁共振（NMR）光谱确定了接枝共聚物的结构。扫描电子显微镜（SEM）显示，与纤维素-PHB共混物相比，纤维素-g-PHB共聚物在纤维素和PHB表面之间形成了连续相。从傅里叶变换红外（FTIR）光谱和X射线衍射（XRD）结果中对纤维素和PHB的相对结晶度进行了定量，同时通过差示扫描量热法（DSC）评估了绝对结晶度。结晶度的降低表明接枝反应不仅发生在纤维素和PHB的无定形区域，也在结晶区域略有发生。较小的晶体尺寸表明PHB的脆性降低。热重分析（TGA）表明接枝共聚物相对于PHB更稳定。通过改变反应参数，有望调控所得纤维素-g-PHB共聚物的组成（%PHB和%纤维素）以获得可调节的性能。
