Thermal analysis of crystallization reveals subtle interactions in pristine graphene-polycaprolactone nanocomposites

IF 3.1 2区 化学 Q2 CHEMISTRY, ANALYTICAL
R. Demoor, L.I. Silva, M. Sosa Morales, C.J. Perez, J.P. Tomba
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Abstract

In this study, we investigate the melting behavior and crystallization of nanocomposites of poly(ε-caprolactone) (PCL), a biodegradable polymer, with pristine graphene, an economically feasible filler widely available from natural sources. Nanocomposites with pristine graphene loads between 0.01 and 5 wt% were prepared via solvent casting and primarily probed by Differential Scanning Calorimetry (DSC). Conventional DSC shows that the presence of graphene increases PCL crystallinity. Non-isothermal crystallization was studied using Mo's model, whereas other parameters as Activation Energy and Nucleation Activity were obtained. It is shown that graphene increases crystallization rates acting as nucleant, with no signatures of retardant effects. Compared with other classic nano-loads, like ad-hoc modified bentonite also analyzed for comparison, pristine graphene is more effective as nucleant, which indicates that it is better dispersed in PCL. Analysis by Self Successive Annealing (SSA), also carried out by DSC, reveals that graphene hinders the formation of crystals with lamellar thickness above 7.3 nm, as found in regular PCL. It may indicate that molecular interactions between PCL and pristine graphene disrupts the movement of polymeric chains, consequently limiting lamellar growth. Evidence of such interaction is found by Infrared and Raman spectroscopies that reveal broadening of the carbonyl peak of PCL and alteration of G and D' bands of graphene.

Abstract Image

结晶热分析揭示了原始石墨烯-聚己内酯纳米复合材料中微妙的相互作用。
在本研究中,我们研究了生物可降解聚合物聚(ε-己内酯)(PCL)与原始石墨烯纳米复合材料的熔融行为和结晶情况,原始石墨烯是一种经济可行的填料,可从天然资源中广泛获取。通过溶剂浇铸法制备了原始石墨烯含量在 0.01 至 5 wt% 之间的纳米复合材料,并主要通过差示扫描量热法(DSC)进行了检测。传统的 DSC 显示,石墨烯的存在会增加 PCL 的结晶度。使用莫氏模型对非等温结晶进行了研究,同时获得了活化能和成核活性等其他参数。结果表明,石墨烯作为成核剂可提高结晶速率,但没有明显的阻滞作用。与其他经典的纳米负载(如也进行了比较分析的临时改性膨润土)相比,原始石墨烯作为成核剂更为有效,这表明它在 PCL 中的分散性更好。同样通过 DSC 进行的自连续退火 (SSA) 分析表明,石墨烯阻碍了片层厚度超过 7.3 nm 的晶体的形成,这在普通 PCL 中也能找到。这可能表明 PCL 和原始石墨烯之间的分子相互作用破坏了聚合物链的运动,从而限制了薄片的生长。红外光谱和拉曼光谱显示 PCL 的羰基峰变宽,石墨烯的 G 和 D'波段发生变化,这些都是这种相互作用的证据。
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来源期刊
Thermochimica Acta
Thermochimica Acta 化学-分析化学
CiteScore
6.50
自引率
8.60%
发文量
210
审稿时长
40 days
期刊介绍: Thermochimica Acta publishes original research contributions covering all aspects of thermoanalytical and calorimetric methods and their application to experimental chemistry, physics, biology and engineering. The journal aims to span the whole range from fundamental research to practical application. The journal focuses on the research that advances physical and analytical science of thermal phenomena. Therefore, the manuscripts are expected to provide important insights into the thermal phenomena studied or to propose significant improvements of analytical or computational techniques employed in thermal studies. Manuscripts that report the results of routine thermal measurements are not suitable for publication in Thermochimica Acta. The journal particularly welcomes papers from newly emerging areas as well as from the traditional strength areas: - New and improved instrumentation and methods - Thermal properties and behavior of materials - Kinetics of thermally stimulated processes
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