Two-Step Freezing in Alkane Monolayers on Colloidal Silica Nanoparticles: From a Stretched-Liquid to an Interface-Frozen State

	Two-Step Freezing in Alkane Monolayers on Colloidal Silica Nanoparticles: From a Stretched-Liquid to an Interface-Frozen State
	Gao, Xia 1; Huber, Patrick 2; Su, Yunlan 1; Zhao, Weiwei 1; Wang, Dujin 1
刊名	JOURNAL OF PHYSICAL CHEMISTRY B
	2016-08-04
卷号	120 期号:30 页码:7522-7528
英文摘要	The crystallization behavior of an archetypical soft/hard hybrid nanocomposite, that is, an n-octadecane C-18/SiO2-nanoparticle composite, was investigated by a combination of differential scanning calorimetry (DSC) and variable-temperature solid-state C-13 nuclear magnetic resonance (VT solid-state C-13 NMR) as a function of silica nanoparticles loading. Two latent heat peaks prior to bulk freezing, observed for composites with high silica loading, indicate that a sizable fraction of C-18 molecules involve two phase transitions unknown from the bulk C-18. Combined with the NMR measurements as well as experiments on alkanes and alkanols at planar amorphous silica surfaces reported in the literature, this phase behavior can be attributed to a transition toward a 2D liquid-like monolayer and subsequently a disorder-to-order transition upon cooling. The second transition results in the formation of a interface-frozen monolayer of alkane molecules with their molecular long axis parallel to the nanoparticles' surface normal. Upon heating, the inverse phase sequence was observed, however, with a sizable thermal hysteresis in accord with the characteristics of the first-order phase transition. A thermodynamic model considering a balance of interfacial bonding, chain stretching elasticity, and entropic effects quantitatively accounts for the observed behavior. Complementary synchrotron-based wide-angle X-ray diffraction (WARD) experiments allow us to document the strong influence of this peculiar interfacial freezing behavior on the surrounding alkane melts and in particular the nucleation of a rotator phase absent in the bulk C-18.
收录类别	SCI
语种	英语
内容类型	期刊论文
源URL	[http://ir.iccas.ac.cn/handle/121111/35238]
专题	化学研究所_工程塑料实验室
作者单位	1.Chinese Acad Sci, Beijing Natl Lab Mol Sci, Inst Chem, Key Lab Engn Plast, Beijing 100190, Peoples R China 2.Hamburg Univ Technol TUHH, Inst Mat Phys & Technol, Eissendorfer Str 42, D-21073 Hamburg, Germany
推荐引用方式 GB/T 7714	Gao, Xia,Huber, Patrick,Su, Yunlan,et al. Two-Step Freezing in Alkane Monolayers on Colloidal Silica Nanoparticles: From a Stretched-Liquid to an Interface-Frozen State[J]. JOURNAL OF PHYSICAL CHEMISTRY B,2016,120(30):7522-7528.
APA	Gao, Xia,Huber, Patrick,Su, Yunlan,Zhao, Weiwei,&Wang, Dujin.(2016).Two-Step Freezing in Alkane Monolayers on Colloidal Silica Nanoparticles: From a Stretched-Liquid to an Interface-Frozen State.JOURNAL OF PHYSICAL CHEMISTRY B,120(30),7522-7528.
MLA	Gao, Xia,et al."Two-Step Freezing in Alkane Monolayers on Colloidal Silica Nanoparticles: From a Stretched-Liquid to an Interface-Frozen State".JOURNAL OF PHYSICAL CHEMISTRY B 120.30(2016):7522-7528.