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ABSTRACT:Montomorillonite was organically modified with three different swelling agents: n-dodecylamine, 12-aminolauric acid, and 1,12-diaminodecane. These organoclays and polyamide 6 (PA6) were blended in a formic acid solution. X-ray diffraction analysis showed that the clay still retained its layer structure in the PA6/clay nanocomposite. Consequently, these materials were intercalated nanocomposites. The effects of the swelling agent and organoclay content on the crystallization behavior of the PA6/clay nanocomposites were studied with differential scanning calorimetry. The results showed that the position and width of the exothermic peak of the PA6/clay nanocomposites were changed during the nonisothermal crystallization process. The clay behaved as a nucleating agent and enhanced the crystallization rate of PA6.The crystallinity of PA6 decreased with an increasing clay content. Different swelling agents also affected the crystallization behavior of PA6. The effects of the type and content of the swelling agent on the tensile and flexural properties of PA6/clay nanocomposites were also investigated.

Low-molecular-weight organogels have applications in several fields, including molecular sensing, [1] nanostructure assembly, [2] and drug delivery. [3] Ideally, these materials would switch reversibly between their solution and gel states through the addition or removal of heat, electrons, or ions.[4] Although these modes of operation are similar to those employed for switches based on interlocked molecules, organogels formed from pseudorotaxane-or rotaxane-type gelators are rare. Indeed, we are aware of only a few previously reported examples, all of which feature long alkyl chains or cholesterol units incorporated into the molecular structures to assist the gelation process.[5] Predicting the molecular structures of potential gelators and their preferred solvents remains difficult, and developing new rotaxane-based gelators that do not feature commonly used types of gelation units (e.g., long alkyl chains, steroids) in their structures is particularly challenging. Herein we report the serendipitous discovery of a urea-based [2]rotaxane that behaves as both a molecular switch and an organogelator; both functions are mediated by acid/base and anion control.The reaction of the macrocycle 1, ] in CD 3 NO 2 shows cross-signals between the ethylene glycol protons of the macrocyclic unit and the aromatic protons of the 3,5-di-tert-butylphenyl stopper adjacent to the DBA + center, however, no crosssignals are seen between the macrocyle and the stopper unit adjacent to the urea station.As expected, addition of potassium tert-butoxide (1 equivalent) to a solution of the [2]rotaxane [5-H][PF 6 ] (CD 3 NO 2 , 13.6 mm) resulted in significant shifts in the locations of many of the signals in the 1 H NMR spectrum (Figure 1). The significant downfield shift of the signal for the macrocyle NH protons, and the appearance of signals for the formerly severely broadened urea protons suggested the formation of hydrogen bonds to the carbonyl group of the urea station (Figure 1 b)

Low-molecular-weight organogels have applications in several fields, including molecular sensing, [1] nanostructure assembly, [2] and drug delivery. [3] Ideally, these materials would switch reversibly between their solution and gel states through the addition or removal of heat, electrons, or ions.[4] Although these modes of operation are similar to those employed for switches based on interlocked molecules, organogels formed from pseudorotaxane-or rotaxane-type gelators are rare. Indeed, we are aware of only a few previously reported examples, all of which feature long alkyl chains or cholesterol units incorporated into the molecular structures to assist the gelation process.[5] Predicting the molecular structures of potential gelators and their preferred solvents remains difficult, and developing new rotaxane-based gelators that do not feature commonly used types of gelation units (e.g., long alkyl chains, steroids) in their structures is particularly challenging. Herein we report the serendipitous discovery of a urea-based [2]rotaxane that behaves as both a molecular switch and an organogelator; both functions are mediated by acid/base and anion control.The reaction of the macrocycle 1, ] in CD 3 NO 2 shows cross-signals between the ethylene glycol protons of the macrocyclic unit and the aromatic protons of the 3,5-di-tert-butylphenyl stopper adjacent to the DBA + center, however, no crosssignals are seen between the macrocyle and the stopper unit adjacent to the urea station.As expected, addition of potassium tert-butoxide (1 equivalent) to a solution of the [2]rotaxane [5-H][PF 6 ] (CD 3 NO 2 , 13.6 mm) resulted in significant shifts in the locations of many of the signals in the 1 H NMR spectrum (Figure 1). The significant downfield shift of the signal for the macrocyle NH protons, and the appearance of signals for the formerly severely broadened urea protons suggested the formation of hydrogen bonds to the carbonyl group of the urea station (Figure 1 b)

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