Microphologies And Their Transition Behaviors Of Linear Triblock Copolymers Under Nanopore Confinements

Copolymers are attributed to one type of macromolecular materials.They can self-assemble into nanostructures. The self-assembledmicrophologies of copolymers are of considerably potential use value invarious fields, such as drug transfer and release，catalyzer, artificialmicrostructure designs as well as nanotechnology. Thus, theself-assembly process of copolymers is attracting more and more interestand attentions. Here, it is an effective method to obtain some novel andspecial nanostructures by inducing copolymer melts into the confinementenvironment. In the paper, the real-space self-consistent field theory isused to investigate microphologies and their transition behaviors of ABClinear triblock copolymers under nanopore confinements. On one hand,the effects of confinement parameters (i.e., diameters of nanopores andsurface fields) and polymer parameters (including volume fractions andinteractions) on microphologies and their transition behaviors are systematically investigated, respectively. On the other hand, under neutralnanopore confinements, the pure geometric frustration morphologies intriangular phase diagrams are studied.For the effects of confinement parameters and polymer parameters,the former ones are firstly studied. For the effect of nanopore dimensions,it is found that: on one hand, under neutral nanopore confinements, thevariations in diameters of narrow nanopores have significant influence onthe self-assembled microphologies of non-cylindrical symmetries.Nevertheless, in the large nanopores case, the self-assembledmicrophologies obviously present cylindrical symmetries andinsensitivity toward the variations in the large pore diameters; on theother hand, under nanopore confinements with strongly preferentialsurface fields, microphologies independent of nanopore diameters presentstrongly cylindrical symmetries. Especially in the strongly A-preferentialsurface field, concentric lamellae independent of nanopore diametersoccur for a series of symmetric triblock copolymers. Secondly, for theeffect of surface field strengths, microphologies are insensitive to thevariations in the B-preferential surface field strength. Whereas thevariations in the A-preferential surface field strength have significantinfluence on microphologies. Especially in the intermediate strengthregion, some complex microphologies occur. Then, the effects of polymerparameters under confinements are studied. First, for the effect of volume fractions under confinements, lots of novel microphologies and thesymmetry nature of phase diagrams are found by using full triangularphase diagrams. Second, for the effect of interaction parameters underconfinements, it is noted that confinements have influence onorder-disorder transition points and order-order transition points.Moreover, in contrast to bulk structures, the confined structures are moresensitive to the subtle variations in interaction parameters.For the investigation on the pure geometric frustrated triangularphase diagrams under neutral nanopore confinements, an appropriatefixed pore diameter is selected. First, it is found that the dominantconcentric lamellae occur so frequently in different phase diagrams.Second, a number of novel and complex microphologies occur in theconfined phase diagrams, in which they present some characteristicfeatures. Third, the symmetry of triangular phase diagrams is againobserved.In summary, by the investigations as mentioned above, it is noted that:the self-assembled microphologies of confined triblock copolymers aredeterminated by the cooperative effects of the commensurability betweenthe diameter of nanopores and the natural period of bulk structures,surface fields, confining boundary geometric shape, polymer parametersand so on. Thus, by controlling the related parameters, some requiredfunctional nanomaterials can be obtained. Simultaneously, we believe that our findings can provide some valuable theoretical guidance for futureexperiments and production industries.