| Supramolecular chemistry is the chemistry that focus on intermolecular non-covalent interactions. The driving force of self-assembly generally comes from intermolecular non-covalent interactions. So usually self-assembly behaviors are all spontaneous and uncontrollable. Stable supramolecular gels can be formed through solvent molecules which bound in the network. Nowadays, the regulation of self-assembly behavior by applying sound, light, electricity, magnetism, heat, ions, redox and other means has caused widespread concern. In addition, the performance of the polymer material can be enhanced in situ by introducing supramolecular aggregates into the polymer matrix. Molecular composite has shown a unique advantage which has been compared with traditional fiber-reinforced composites.The aqueous solution of the triblock polymer can be gelled by taking advantage of hydrogelator. The hydrogelator aggregates phase behaviour can be turned from3D to2D while the aqueous solution of the triblock polymer bacome lamellar structure within a specific temperature range. So the self-assembly behaviour of hydrogelator can be controlled by tuning the temperature. A series of molecular composites were prepared by introducing organic gelator and organic-metal aggregates into polyurethane matrix. The molecular reinforce effect and the mechanism of gelator aggregates enhance polymer was studied.This thesis is consisted of several sections as the following:1. This work took advantage of the PEO-PPO-PEO three block copolymer aqueous solution (PE6200) which had phase transition properties that from isotropy micellar phase to anisotropic lamellar at specific temperatures. The self-assembly behavior of gelator in PE6200water system was studied by introducing the hydrogelator (HB21) that contains1,2,4,5-benzenetetracarboxylic acid and4-hydroxypyridine (1:2) into the aqueous system. Small Angle X-ray scattering (SAXS) results showed that PE6200water system became isotropic liquid, gelator self-assembled to form stable three-dimensional network structure, in the temperature range less than50℃. While warned up to50～60℃, gelator aggregates transformed into two-dimensional self-assembly structures in PE6200polarized area rich in water, beause the hydrophilic factor and the stability of the system entropy PE6200into lamellar structure. Scanning differential calorimeter (DSC), variable temperature Raman spectroscopy and electrochemical cyclic voltammetry characterization, further confirmed the phase transition behavior in the temperature range. These results suggest that gelator from3D to2D self-assembly is a process of thermodynamic controlled. Thus put forward a way to tune self-assembly behaviour by taking advantage of thermodynamics controllable block copolymer.2. Nanometer fibrous aggregates which formed by organic gelator1,3:2,4-Dibenzylidene sorbitol (DBS) were introduced into a conventional modified polyurethane resin (SM6202). Through the principle of molecular composite, organic gelator DBS gelled the precursor polymer resin first and then the gel polymerized by UV initiate to prepare molecular composite polymer. The results showed that DBS in the oligomer matrix resin had excellent gelation performance, DBS supramolecular aggregates formed nano fibrous confirmed by SEM. The elongation at break and tensile fracture strength of composites increased significantly, which was demonstrated by stress-strain curve of composite material that contained DBS aggregate and modified polyurethane. The elongation at break increased from31%to45%with a growth of50%, the tensile breaking strength increased from1.4MPa to4.2MPa with a growth of200%. The composites material with DBS became toughening and strengthening on the macroscopic. The influence of inherent modulus of the composite material and glass transition temperature of the system with DBS aggregates were characterized by dynamic mechanical thermal analysis (DMA). In addition, the specific gravity and transparency test showed that DBS composites in situ not only enhanced mechanical properties but also maintained the characteristics of light weight and high transparency of polymer materials. The results demonstrated the unique advantages which compared to the traditional macro-fiber composites.3. Polyurethane oligomer (SM6202) was gelled by Fe(III) and sebacic acid which formed compounds Fe(SA). The preparation of molecular composite polymer was carried out by UV-light initiate. The SEM results showed that the Fe(SA) became spherical aggregates which formed by curly lamellar. The elongation at break and tensile fracture strength of polyurethane composites were improved significantly. The elongation at break increased from31%to53%with a growth of71%, the tensile breaking strength increased from1.4MPa to4.3MPa with a growth of207%. The composite material bacame toughening and strengthening on the macroscopic. The storage modulus and glass transition temperature of Fe(SA) composites increaseed which was confirmed by dynamic mechanical thermal analysis (DMA). In addition, the specific gravity and transparency test showed that Fe(SA) composites in situ not only enhanced mechanical properties but also maintained the characteristics of light weight and high transparency of polymer materials. The results demonstrated the unique advantages which compared to the nano-particulate filler. |
PDF Full Text Request