Dimensianal Control And Morphology Investigation In Solution Self-Assembly Of Conjugated Block Copolymers

"Bottom-up" approach of self-assembly has become a new kind of preparation method of micro-/nano-materials in recent years due to its various advantages including low energy consumption,easy to repeat,low cost and easy operation,which has attracted extensive concerns of the researchers.This method has been utilized to prepare micro-/nano-materials with different functions and structures.We have seen a few dramatic breakthroughs in the formation of 2D highly symmetrical supramolecular structures with considerable control.However,the preparation of stable 1D or 2D micelles with precise control on morphology and dimension remains a key challenge.Here we present a simple approach for the preparation of fluorescent non-crystallization micelles with different dimensions and structures using conjugated block copolymers?BCP?PPV₉-b-P2VP_n through a simple process of"dissolving–cooling–aging".The morphology and dimension control of the final assembly structure can be achieved by adjusting the block ratio of the copolymer,the side chain groups of the PPV segments and the type of solvents.The results reveal that the micelles of PPV₉-b-P2VP_n initially form 1D tiny line structure and then grow into final structures in solution,including the transformation from 1D to2D.Meanwhile,we also prove that the growth is driven by intermolecular?–?stacking interactions between the PPV₉ blocks.The main content of this work will be shown in the following four parts.The first,we designed and synthesized a series of supramolecular amphiphilic BCPs composed of a core-forming ?-conjugated block of poly?2,5-di?2?-ethylhexyloxy?-1,4-phenylenevinylene??PPV?and a corona block of P2VP.By ¹HNMR and GPC characterizations,the monomer number of PPV block was calculated and the different block ratios could be confirmed.Second,Through the concise process of"dissolving–cooling–aging",different dimensional architectures consist of line,ribbon,"inky-flower"and particular"scarf"micelles which rarely appears in non-crystallization self-assembly system were yielded.The assembly morphology and dimension could be affected by the block ratios of BCPs,the side chain groups of PPV segment and the type of solvents.At the same time,the influence of solvent to assembly speed has also been studied.In addition,samples with different PPV side chains were mixed into the solution to grow together,we find that they have a distinct identification effect.Third,by in-situ following the growth process of different samples in different solution,we find that although there are great differences in the resulting morphology,the growth process presents a large consistency.All micelles of PPV₉-b-P2VP_n initially form 1D tiny line structure and then grow into final structures in solution,including the transformation from 1D to 2D.And finally,based on the characterization of UV-Vis absorption,we studied the spectral change with temperature and aging time.The blue-shift of adsorption reveals that the self-assembly of micelles was driven by H-aggregation of the PPV₉blocks.It also proves that the driven force is one of the non-crystalline interactions-?–?stacking interaction.Furthermore,we find that the aggregation of amphiphilic PPV₉-b-P2VP_n in solution has close relation to temperature.In summary,we have described a simple strategy for preparing different micro-/nano-dimensional structures of PPV₉-b-P2VP_n BCPs through intermolecular?-?stacking interaction and hydrophobic interaction.This strategy is practical and expected to be easily applicable to other BCPs systems,which can broaden the scope of self-assembly and is expected to achieve hierarchical self-assembly in a certain degree like the reported crystallization driven self-assembly system.Moreover,these different morphological micelles possess high stability,flexibility,large surface-to-volume ratios,definite fluorescent efficiency and the ability of functionalization.Therefore,they have attractive potential in applications such as biosensors,catalysis,template building,optoelectronics,biological imaging,cancer therapy and other domains.