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Reactive two-dimensional layered material with regular chlorine groups

https://doi.org/10.1016/j.jcis.2007.06.019Get rights and content

Abstract

A novel reactive layered two-dimensional molecular space material [layered chloroacetamide phenyl silica (CAAPhS)] with regular chlorine groups was synthesized by grafting chlorine groups into the layer structure of layered aminophenyl silica. The reactive activity of chlorine groups regularly arranged in the layer structure of layered CAAPhS was confirmed through a substitution reaction with n-butylamine. Layered CAAPhS showed potential as a starting material for the formation of a series of two-dimensional layered materials with various regular functional molecules and organic–inorganic composite materials.

Introduction

Nanospace materials can be used to influence and control chemical processes in their nanospaces, because they provide molecular reaction spaces with special properties. Layered materials, such as clay minerals and layered double hydroxides (LDHs), have been investigated extensively as nanospace materials, as they provide stable two-dimensional nanospaces for chemical processes [1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19], [20], [21], [22], [23], [24], [25], [26], [27], [28], [29], [30], [31], [32], [33], [34], [35], [36], [37], [38], [39], [40], [41], [42]. A variety of molecules can be intercalated into the two-dimensional interlayer spaces of layered materials. The two-dimensional layer structure of layered materials is expandable with the size of the intercalated molecule. The intercalated molecules can form monolayers or bilayers in the interlayer spaces of layered materials independent of molecular size, due to the interaction between the layer plate and the molecule. Therefore, two-dimensional layered materials are promising materials for influencing and controlling molecular reaction processes in interlayer spaces.

However, it is difficult to influence and control molecular reaction processes in interlayer spaces utilizing current layered materials due to a lack of functional properties and an unchangeable layer structure. If we can develop a series of two-dimensional layered materials with regular functional groups in the layer structure, the molecular reaction processes will be influenced and controlled in the two-dimensional molecular spaces through the interaction between regular functional groups and the guest molecules. The regular arrangement of functional groups is a key point for influencing and controlling molecular reactions in the two-dimensional molecular space. A regular arrangement of functional groups in the two-dimensional structure would form a controllable molecular reaction space. Therefore, it is very interesting to synthesize two-dimensional layered materials with regular functional groups in the layer structure.

Previously, we reported a novel layered aminophenyl silica material (C12H25OSO3+/NH+3C6H4SiO1.5, APhTMS-DS) with amino groups in the layer structure [43], [44]. The layered APhTMS-DS with regular amino groups exhibited a stable layer structure and a better intercalation response. We also have developed a novel two-dimensional molecular space material with regular double bonds by modifying the layered aminophenyl silica with acrylic acid [45]. The polymerization processes and structure of acrylic acid were found to be influenced and controlled by the regular two-dimensional molecular space [46]. The novel two-dimensional molecular space with regular functional groups in structure showed potential for influencing and controlling molecular reaction processes. Therefore, it is important to further develop a series of two-dimensional layered materials with various regular organic functional groups in a layer structure and find more examples of influencing and controlling molecular reaction processes utilizing regular two-dimensional molecular spaces.

Here, we report the development of a novel two-dimensional layered material with regular chlorine groups (layered chloroacetamide phenyl silica, CAAPhS) by grafting chlorine groups in the layer structure of layered aminophenyl silica. Chlorine groups regularly arranged in a two-dimensional layer space can undergo substitution reactions with other organic molecules and can be initiators in controlled free radical polymerization [47]. Thus, two-dimensional layered materials with regular chlorine groups can be important starting materials for synthesizing a series of two-dimensional layered materials with various regular functional molecules in their layer structure and a series of novel organic–inorganic nanocomposite polymer materials.

Section snippets

Experimental

All the reagents were purchased from the Aldrich Chemical Co. and used as received. Layered aminophenyl silica (APhTMS-DS) was synthesized by the slow titration of HCl into a mixture of p-aminophenyltrimethoxysilane (APhTMS, 2.78 mmol) and SDS (2.92 mmol) in aqueous solution with stirring at room temperature (pH 2–3). APhTMS–dodecyl sulfate complex (APhTMS-DS) was obtained as a light pink precipitate.

Layered CAAPhS was synthesized by mixing 0.2 g APhTMS-DS and 4 mmol chloroacetyl chloride in 30

Results and discussion

The IR spectra of CAAPhS and APhTMS-DS are shown in Fig. 1. A new peak at 1672 cm−1 was observed in the IR spectrum of CAAPhS compared with layered APhTMS-DS. The peak at 1672 cm−1 was assigned to carbonyl in amide formed between the amino groups of layered APhTMS-DS and acyl chloride groups of chloroacetyl chloride. The stronger vibration peaks (3000–2800 cm−1) of methylenes of DS (dodecyl sulfate) in the IR spectrum of layered APhTMS-DS (Fig. 1a) were not observed in CAAPhS (Fig. 1b). The SDS

Conclusions

A novel two-dimensional molecular space material with regular chlorine groups was synthesized by liquid–solid reaction between layered APhTMS-DS and chloroacetyl chloride. The results of IR spectrum, XRD pattern, and SEM micrograph indicated that layered CAAPhS has functional regular chlorine groups and a stable layer structure, as shown in Scheme 1. The results of elemental analyses also further confirmed that the amino groups in layered APhTMS-DS were almost completely transformed to amide

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