Self-assembled Morphologies And Thermal Analysis Of Block Copolymers

In this thesis, the study mainly includes the following three aspects:(?) self-assembly of ABC dendrimer by real-space self-consistent mean field theory; (?) self-assembly of ABC star triblock copolymer thin films confined with a preferential surface:a self-consistent mean field theory; (?) synthesis and thermal analysis of linear triblock copolymers based on methacrylate ester.In the first part, we systematically studied the phase behavior of ABC dendrimer melt systems by real-space implementation of self-consistent mean field theory, and compared it with linear, star ABC triblock copolymer to find the major influences of different chain topology. Seven ordered morphologies have been observed during the simulation. They are (a) dodecagon-hexagon-tetragon (DOHT. [12.6.4]); (b) "three-color" lamellae phase (LAM3); (c) core-shell hexagonal lattice phase (CSH); (d) "three-color" hexagonal honeycomb phase (HEX3); (e) decagon-hexagon-tetragon, decagon-hexagon-hexagon phase (DEHT, DEHH. [10.6.4; 10.6.6]); (f) lamellae phase with alternating beads (LAM+BD); (g) octagon-octagon-tetragon phase (OOT. [8.8.4]). Most of them present in the simulation of linear or star ABC triblock copolymer; however, the DOHT is particular in ABC dendrimer.Triangle phase diagrams are constructed for three classes of typical ABC dendrimer in terms of the relative strength of the interaction parameters:symmetric interaction parameters xABN=xACN=xBCN=80 and asymmetric interaction parameters one, xABN=80, xACN= XBCN=100. When the volume fraction and interaction energies of the three species are comparable, the HEX3 phase is found to be the most stable. Near the region of HEX3 in the triangle phase diagrams, we found another competitive microphase (OOT) with its energy is close to HEX3. The DOHT phase is first reported in the ABC dendrimer, and the decagon-hexagon-tetragon, decagon-hexagon-hexagon phase ([10.6.4; 10.6.6]) mixed phase is complementary shown as a microphase with asymmetric center. When the volume of one species is big enough, such as fA(or fB,fc)?0.7, the chain topology of dendrimer do not stretch as it want to be, then it takes a LAM+BD microphase as linear ABC triblock copolymers.In the second part, microphase separation and morphology of a near-symmetric A0.3B0.3C0.4 star triblock copolymer thin film confined between two parallel and homogeneous hard walls have been investigated by self-consistent mean field theory (SCMFT) with a pseudo-spectral method. Our simulation experiments reveal that under surface confinement, in addition to the typically parallel, perpendicular, and tilted cylinders, other phases, such as lamellae, perforated lamellae, and complex hybrid phases, have been found to be stable, which are attributed to the block-substrate interactions. Especially those hybrid phases in which A block and B block disperse as spheres and alternately arrange as cubic CsCl structures, with a network perforative structure of C block. The results show that these hybrid phases are also stable within a broad hybrid region (H-region) under suitable film thickness and broad field strength of substrates, due to their free energies is too close to being distinguished. Phase diagrams have been evaluated by purposefully and systematically varying the film thickness and field strength at three different cases of Flory-Huggins interaction parameters between species in the star polymer. We also compare the phase diagrams for weak and strong preferential substrates, each with a couple of opposite quality and discuss the influence of confinement, substrate preference, and the nature of the star polymer on the stability of relatively thinner and thick film phases in this work.In the third part, Two linear triblock copolymer:poly(t-butyl methacrylate-b-glycidyl methacrylate-b-styrene) with equivalent arms (PtBMA97-b-PGMA18-b-PSt98), and poly(t-butyl methacrylate-b-2-hydroxyl ethyl methacrylate-b-N,N-dimethylamino-ethyl methacrylate) with unequal arms (PtBMA137-b-PHEMA23-b-PDMAEMA156) were controlled synthesized with living RAFT polymerization technique under the chain transfer of cumyl dithiobenzoate. The results of FT-IR spectra illuminates that the characteristic groups of copolymer fit well with the result of 1H-NMR which successfully determine the corresponding molecular structure of triblock copolymers. The thermal stability of PtBMA97-b-PGMA18-b-PSt98 and PtBMA137-b-PHEMA23-b-PDMAEMA156 were also complementarily explained by the activation energy of thermal decomposition from Friedman differential method and Ozawa-Flynn-Wall integral method. The results show that the degradation energy of the former copolymer was much higher than that of the latter copolymer due to the aromatic groups were introduced into the polymer segments of the former copolymer during the RAFT polymerization process and because of the oxirane rings are typically reactive, that they occurred intermolecular crosslinking reaction during the thermal decomposition.