Block Copolymers - Morphology

Small angle neutron scattering (SANS) and neutron reflectivity (NR) have also been used to characterize the morphology and scattering from PDMA- 

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Since excellent reviews on block copolymer crystallization have been published recently [43,44], we have concentrated in this paper on aspects that have not been previously considered in these references. In particular, previous reviews have focused mostly on AB diblock copolymers with one crystal-lizable block, and particular emphasis has been placed in the phase behavior, crystal structure, morphology and chain orientation within MD structures. In this review, we will concentrate on aspects such as thermal properties and their relationship to the block copolymer morphology. Furthermore, the nucleation, crystallization and morphology of more complex materials like double-crystalline AB diblock copolymers and ABC triblock copolymers with one or two crystallizable blocks will be considered in detail. 

Choucair A, Eisenberg A. Control of amphiphilic block copolymer morphologies using solution conditions. Fur Phys J Eng 2003 10 37-44. 

Light microscopy has been used in a number of contexts to characterize block copolymer morphology. For crystalline block copolymers, spherulitic structures that result from organization of crystalline lamellae can be examined using microscopy. In solutions, polarized light microscopy can reveal the presence of lamellar and hexagonal-packed cylindrical micellar phases. Cubic micellar phases are optically isotropic, and consequently cannot be distinguished from sols only on the basis of microscopy. 

When a chemical variety of a linear block copolymer is increased to three different components, an intricate diversity of structures becomes possible [188, 189], This is due to considerable increase in the number of involved polymer-polymer and polymer-surfaces interaction parameters. The studies on thin film behavior of ABC terpolymers are rare, even though they may potentially be more versatile than binary block copolymer morphologies due to the increased complexity. 

FIGURE 2.6. Block copolymer morphologies obtainable via phase separation. The exact structure will depend on the relative volume fractions of the two blocks, as well as /N (where / is the interaction parameter and N the length of the polymer). 

Block copolymer morphologies have been studied in great detail predictive relationships between molecular structure and equilibrium bulk morphology have been developed and thoroughly tested against experimental observations. 

Increasing volume traction of minority phase Fig. 1. Block copolymer morphologies... 

Fig. 15.3. Schematic depiction of the geometric arguments for prediction of block copolymer morphology. (Adapted from [1].)...

Thermodynamic treatments of block copolymer morphology, such as those of Helfand (1,2,3) and Meier (4), which are based on anionically polymerized, monodisperse segment AB and ABA type block copolymers, are not applicable in the present case. The large number of short segments in each molecule, the possibility of crystallinity in one or both phases, and the likelihood of metastable morphologies work together to preclude the analytical approaches presently available. 

The introduction of functional groups at the end(s) or along the polymer chain can produce new materials that can be used as models to study and manipulate fundamental phenomena in polymer science, such as association, adsorption, chain dynamics, and block copolymer morphology.61 65 The synthesis of end-functionalized polymers remains a challenging problem in polymer chemistry. Among the different... 

Gratt JA, Cohen RE (2004) The role of ordered block copolymer morphology in the performance of organic/inorganic photovoltaic devices. J Appl Polym Sci 91 3362-3368 Sun S, Fan Z, Wang Y, Haliburton J (2005) Organic solar cell optimizations. J Mater... 

Tri-block copolymer morphologies (a) Three-dimensional reconstruction of TEM images of gyroid structure in styrene isoprene styrene (Spontak, R. J. and Patel, N. P., Curr. Opin. Coll. Interface Sci, S, 334, 2000) Elsevier (b) TEM of lamellar edges in styrene butadiene styrene (Huy, T. A. et al.. Polymer, 44, 1237, 2000) Elsevier. 

Lazzari M, De Rosa C. 2006. Method for the alignment and the large scale ordering of block copolymer morphologies. In Lazzari M, Liu G, Lecommandoux S, editors. Block Copolymers in Nanoscience. Weinheim Wiley VCH. pp. 191 231. 

Meier [23] has derived equations relating block copolymer morphology to thermodynamics using lattice models. His model explains quantitatively the observations of Merrett [24] on the influence of preferential solvents on the mechanical properties of graft copolymers. Merrett found that, depending on the solvent used in casting films of a natural rubber/poly(methyl methacrylate) graft copolymer, he could obtain either a hard stiff film characteristic of poly(methyl methacrylate) or a soft, flexible film typical of natural rubber. He interpreted these results as follows a solvent for poly(methyl methacrylate) collapsed the... 

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