The Synthesis And Self-Assembly Of Novel Giant Molecules With Ultra-Small Phase-Separated Domain Sizes

To overcome the physical limit and the high costs problem of conventional“top-down”lithographical methods,alternative nanopatterning technologies should be developed.The“bottom-up”method has received a great concern due to its ability to self-assemble into lamellar and hexagonal structures with sub-10 nanometer(nm)feature sizes.However,achieving lamellar or hexagonal structure with sub-5 nm feature sizes and corresponding self-assembling materials with the excellent thermal stability,remains a great challenge in the field of self-assembly.Herein,resorting to the guide of crystallization-driven thought,we have achieved the3 nm feature size of lamellar phase,which is the smallest one in the field of macromolecular bulk self-assembly.In addition,we further crosslinked and sonicated the lamellar structure,and successfully prepared nanosheets with sub-10 nm thickness.The main contents and results of this research are as follows:1.We have synthesized a series of novel giant molecules(GMs)composed of crystalline vinyl polyhedral oligomeric silsesquioxane(VPOSS)and precise oligo L-lactic acid(o LLA).These novel GMs displayed better thermal stability than small liquid crystals,and the assembled domain size of lamellar phase can be low down to 3 nm,which is hard to achieve by using high?block copolymers(BCPs)and BCPs with complicated topological structures.In addition,further investigation indicates that the driving force of these GMs originates from the crystalline VPOSS.Combining the calculation of cross-sectional areas of VPOSS and o LLA,we receive the packing model of these GMs.2.We further crosslinked and sonicated the lamellar GMs to prepare nanosheets.The results showed that the method using?-ray and removing o LLA under high temperature was better than others used.By without adding any solvent,we did not find good nanosheets by using thermal crosslinking and light-induced crosslinking;we found many nanosheets in the product of VPOSS-o LLA₁₆ using?-ray crosslinking.To further investigate the efficiency of removing o LLA by using n-hexylamine(an organic weak base),potassium carbonate(an inorganic weak base),and high temperature,we find that the efficiency of using high temperature is good.Finally,many nanosheets can be obtained in VPOSS-o LLA₁₆ when it is crosslinked in 500 k Gy doses,and then treated in 400?and the following sonication.The 3 nm domain size using crystallization-driven novel GMs is the smallest one in the field of macromolecular bulk self-assembly.Moreover,the crystallization-driven self-assembly provides a new strategy for achieving sub-5 nm feature sizes in the bulk self-assembly.Considering the high etching contrast endowed by the high silicon content of novel GMs,this system is promising for achieving further nanopatterning.The method using?-ray crosslinking and pyrolyzing o LLA,which is not reported previously,has provided a new thought for preparing two dimensional(2D)nanomaterials,even for functionally multi-dimensional nanomaterials.