New Design,Synthesis And Property Of Giant Molecules Based On Pentiptycene,POSS And [60] Fullerene

Since H.Staundinger proposed the concept “macromolecules”,polymer science has been developed tremendously: they now serve as a vital part of our life and society.Nevertheless,it is still a great challenge to synthesize macromolecules precisely and efficiently,and control their hierarchical structures for desired materials with specific properties.Giant molecules are the precisely defined macromolecules made from molecular nanosized particles(MNPs)or its conjugates with other molecular nanobuilding blocks including polymers and dendrimers.Fullerene,polyhedral oligomeric silsesquioxanes(POSS)and polyoxometalates(POM)are common MNPs.These MNPs are of precisely modified sites and they could be linked to constitute giant molecules by click reactions.The obtained giant molecules are able to generate complex hierarchical structures like Frank-Kasper phases and DQC(10-fold two-dimensional decagonal quasicrystal)phase.The formed structures are sensitive to plenty of internal and external parameters such as surface properties of those MNPs,the volume ratio between MNPs in a molecule,the linker length and flexibility as well as interfacial property between MNPs,the mole ratio of different giant molecules,concentration,temperature,etc.Giant molecules with the toolbox of “molecular lego” approach could provide a robust platform to design and construct precise macromolecules.Nevertheless,there are only a small handful library of MNPs reported until now like POM,POSS and [60]fullerene(C60).In this dissertation,we firstly try to prepare a novel generation of MNPs using pentiptycenes,which is essential to enrich MNPs for more unique giant molecules.The modified pentiptycene skeletons with orthogonally reactive sites and instinct D2 h symmetry are used here to construct giant moelcules for the first time.Combining new pentiptycene skeletons with POSS and C60,new giant molecules including giant chain molecules,giant molecular patchy particles,giant surfactants and giant ions could be designed and synthesized successfully.Moreover,these new giant molecules are found to be with unique properties.The main content and conclusion of this dissertation are shown in the below:(1)The modification of the MNPs including pentiptycene,POSS and C60 to constitute the giant chain molecules,giant molecular patchy particles,giant surfactants,giant ions and etc.Firstly,the new modified pentiptycene is with orthogonal reaction sites.Two kinds of functionalizations on the pherpherial positions of the new pentiptycene have been successfully realized by Sonogashira reaction and Suzuki reaction.The two reactions could help to get two kinds of penptiptycenes with latent hydrophilic groups and hydrophobic groups respectively.Combining the iterative exponential growth approach and stepwise iterative method,two kinds of pentiptycenes could be linked precisely to get eight giant chain molecules with defined composition and sequence.Different kinds of POSS groups have been synthesized and linked onto the new pentiptycene sketelon by click reaction to get VOV-type(with vinyl POSS cages on the two sides of the pentiptycene)and DOD-type(POSS cages with hydroxyl groups on the two sides of the pentiptycene)giant molecular patchy particles.Ten kinds of giant surfactants with different heads and tails could be got by functionalizing the peripheral eight sites with different groups and attaching polystyrene tails with varied length onto the para-positions of the pentiptycene.Successfully-explored mono-and multi-functionalization of C60 make it possible to synthesize different kinds of giant molecules including giant ions.(2)The property at air-water interface of sequence-defined giant chain molecules.The property at air-water interface is explored by the Langmuir-Blodgett technique and the kinetic Monte Carlo(k MC)scheme.When the mean molecular area(MMA)is high,these molecules aggregate at the air-water interface to form continent-like monolayer films.The degree of the orientation of these molecules in monolayer films is related to their composition and sequence.Upon compressing,the degree of the orientation is increased.The formed continents would collide with each other and become into smaller pieces,after which there would form holes among the monolayer films due to the irregular shapes of these continents and pieces.There are chain rearrangements after transferring the monolayer films onto the solid substrate when the MMA is high.When the MMA is low,there is no apparent rearrangements due to dense packing and the thickness of the monolayer film is dependent on the composition and sequence.Among the monolayer film especially the hydrophobic part,it is disorder but the molecular rearrangements change constantly during compressing.The change rate is increased as the MMA decreases and the change patterns are also related to the composition and sequence.(3)The mesostructures formed by giant molecular patchy particles.For VOV-type giant molecular patchy particles,the molecules VOV,2VOV and 3VOV form the A15 phase and the basic unit for A15 phase is the polyhedra formed by two giant molecular patchy particles.The size of the formed A15 lattice is increased when the number of VPOSS(POSS cages with vinyl groups)in the molecules increases.It is disorder for 4VOV.For DOD-type giant molecular patchy particles,it is body-centered cubic(BCC)phase for the molecule DOD.The polyhedra packing into BCC phase is constituted of nine of the molecules.The molecule 2DOD formed double gyroids(DG)phase where DPOSS cages(POSS cages with hydroxyl groups)and OPOSS cages(POSS cages with alkyl groups)formed two continuous phases respectively.For molecules 3DOD and 4DOD,they all formed HEX phases.There are three molecules in one layer for 3DOD and the molecule adopts a fan-like shape with the fan angle 120°.For 4DOD,the molecule adopts a fan-like shape with the fan angle 180° and there are two molecules in one layer.These self-assembly behaviors show the effects of patchy property and patch size on the self-assembled structures.(4)The self-assembly property of the giant surfactants.The giant surfactants with fluorocarbon chains as the head would aggregate in the tetrahydrofuran and there is phase separation between the fluorocarbon chain and the polystyrene part in lager aggregates.By adjusting the length of polystyrene chain,they would form lamella(LAM)phase,hexagonal(HEX)phase and BCC phase.Due to the special nature of this kind of giant surfactants,the dspacing of the formed LAM phase and HEX phase would increase and then decrease as the temperature ramps.For the BCC phase,the giant surfactants would adopt a cone-like shape and there are around 33 molecules in a polyhedron.This work shows how to control the hierarchical structures and their properties by tuning the tail length of the giant surfactants.(5)The dielectric property of C60 derivatives including giant ions.In solution,there is the deshielding effect of the fullerene core for hydrogen atoms around the hexakis-adducts of C60.The self-diffusion coefficient in solution of the functional groups on fullerene derivatives is much lower than small solvent molecules.It would increase the dielectric constant without causing higher loss by adding giant ions into the resin.By comparing with the dielectric results of small ions and other C60 derivatives,we found giant ions could not move across a long distance in the resin because of large size and this led to higher dielectric constant but low loss at lower frequency region.The C60 core would interact with the matix and induce larger polarization to increase the dielectric constant at higher frequency region.