Two-component gelator

A dendritic two-component gelator was synthesised by Smith et al. on the basis of self-assembling acid-base/hydrogen bond interactions. Dendritic lysine building blocks serve as dendrons, and an aliphatic diamine as core (Fig. 2.12). Depending upon the choice of building blocks, the supramolecular complex forms fibrous gel phases by hierarchic self-organisation. 

Fig. 2.12 Dendritic two-component gelator produced by supramolecular synthesis (according to Smith et a/.) stereocentres are marked red...

Fig. 2.25 Motif of complementary intermolecular hydrogen bonding of two-component gelators.

The motif of complementary intermolecular hydrogen bonding is shown in Fig. 2.25. The molecular arrays based on complementary intermolecular hydrogen bonding is formed, but the branched alkyl chains of the two components are randomly folded and bent, in contrast to the extended alkyl chains of cocrystals. Besides 76+77 and 78+79, some other two-component gelators have been report-... 

Fig. 12 Structure of two-component gelation system based on the interaction between 78 and diaminoundecane...

In early 2001, Smith and co-workers communicated the basic design principles of the first dendritic two-component gelator [70]. This system was based... 

This system has been investigated in detail, and the tunability of this type of two-component gelation system has been exemplified, as explained below. The acid-base interaction between the two components plays a primary role in the formation of the gel—if the acid is protected as an ester, no gel formation takes place. It is proposed that this interaction (Fig. 20) generates the gelator complex, which is the species that hierarchically self-assembles to form fibrous gel-phase aggregates. Interestingly, it was reported that macroscopic gelation still occurred when the acid-base interaction was swapped for an interaction between a crown ether and a protonated amine (Fig. 21) [71]. This indicates that different supramolecular interactions between the components can easily be employed. 

Fig. 23 The nanoscale morphology observed using SEM for the two-component gelation system, a = 2 1 dendron diamine ratio, b = 1 4.5 dendron diamine ratio...

Fig. 25 First A and second B generation dendrons capable of acting both as one- and two-component gelators. Dendron B is a more effective one-component gelator, whilst dendron A forms stronger gels in the presence of a second component (diaminodode-cane)...

The clear-coat is referred to as a two-component (2K) clear-coat when isocyanate is used as the cross-linker. The isocyanate must be added to the hydroxy functional acrylic just prior to spray application to prevent premature cross-linking (or gelation). For this reason, the two-part mixing is referred to as 2K. Cure conditions for isocyanate-cured clear-coat range from room temperature (car refinish) to 250°F for 30 min. 

Experiments were centered around conditions that would result in simultaneous polymerization or simultaneous gelation of the two components. Reactions off center resulted in one reaction or the other proceeding faster. Thus a range of properties at or near simultaneous gelation could be systematically observed. The range of the initiator concentration was 0.18-0.46% (based on n-butyl acrylate). The epoxy was prereacted from one to eleven hours before the acrylate mix was added. 

Figure 1.11 Schematic diagram showing the formation of a microporous system by thermal gelation of a two-component mixture exhibiting a miscibility gap at Certain conditions of temperature and composition,...

Gelation Time Measurement. A modified method from that described in ASTM D2471 was adopted for the measurement of gelation time for this new resin system. Epoxy-episulflde resin and Versamid 140 were weighed into separate regions of one small aluminum dish and brought to room temperature (23 C). The two resins were not permitted to contact each other in the dish. The two components were then mixed thoroughly for 30 sec. by the use of a spatula. 

The combination of 78+79 could gel Az-propanol, chloroform, benzene, ethyl acetate and acetone. The important feature of the two-component type of gelator is the fact that heating is unnecessary for the preparation of the gel, if it dissolves at... 

There exist however also complex gels in which the two components form an intertwined gel structure which structures have struck up complex relations between one another (for example gelated mixture of gelatin and agar sols, placed in an acid medium). 

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