Microphases separated structure

ABA type poly(hydroxyethyl methacrylate) (HEMA) and PDMS copolymers were synthesized by the coupling reactions of preformed a,co-isocyanate terminated PDMS oligomers and amine-terminated HEMA macromonomers312). Polymerization reactions were conducted in DMF solution at 0 °C. Products were purified by precipitation in diethyl ether to remove unreacted PDMS oligomers. After dissolving in DMF/toluene mixture, copolymers were reprecipitated in methanol/water mixture to remove unreacted HEMA oligomers. Microphase separated structures were observed under transmission electron microscope, using osmium tetroxide stained thin copolymer films. 

Dielectric relaxation studies of phosphorylated polyethers from — 180° to 200 °C have been used to study their structures. The magnitude of the dielectric constants of high-phosphonic-acid-content polymers is much larger than predicted, which suggests a microphase-separated structure. Conductance studies on some aryl- and alkyl-phosphonium salts showed a higher conductance for the halides than for the nitrate. ... 

The formation of nanopattemed functional surfaces is a recent topic in nanotechnology. As is widely known, diblock copolymers, which consist of two different types of polymer chains cormected by a chemical bond, have a wide variety of microphase separation structures, such as spheres, cylinders, and lamellae, on the nanoscale, and are expected to be new functional materials with nanostructures. Further modification of the nanostructures is also useful for obtaining new functional materials. In addition, utilization of nanopartides of an organic dye is also a topic of interest in nanotechnology. 

Secondly, we describe the site-selective introduction of a functional molecule, tetrakis-5,10,15,20-(4-carboxyphenyl)porphyrin (TCPP), into the microphase separation structure of a diblock copolymer film of PS-fo-P4VP. Since porphyrin derivatives show various functionalities such as sensitization, redox activity, and nonlinear optical effect, a polymer nanodot array containing a porphyrin at a high concentration would be applicable to a light-harvesing and charge transporting nanochannel. 

As aforementioned, diblock copolymer films have a wide variety of nanosized microphase separation structures such as spheres, cylinders, and lamellae. As described in the above subsection, photofunctional chromophores were able to be doped site-selectively into the nanoscale microdomain structures of the diblock copolymer films, resulting in nanoscale surface morphological change of the doped films. The further modification of the nanostructures is useful for obtaining new functional materials. Hence, in order to create further surface morphological change of the nanoscale microdomain structures, dopant-induced laser ablation is applied to the site-selectively doped diblock polymer films. 

Funaki, Y, Kumano, K., Nakao, X, Jinnai, H., Yoshida, H., Kimishima, K., Xsutsumi, K., Hirokawa, Y. and Hashimoto, X. (1999) Influence of casting solvents on microphase-separated structures of poly(2-vinylpyridine)-fcJocfe-polyisoprene. Polymer, 40, 7147-7156. 

Table II shows Tgs obtained from DSC traces. (Footnotes a and b in Table II show T s values of three reference polymers two PIBs, whose Mns are similar to the Mns of MA-PIB-MA used in the network synthesis, and a PDMAAm the difference in the Tg for the Mn=4,000 and 9,300 PIBs is due to the dependence of Tg on Mn(72)). The DSC traces of the networks exhibited two Tgs, one in the range of -63 to -52 °C (PIB domains) and another in the range of 90 to 115 °C (PDMAAm domains) indicating microphase separated structures. The Tgs associated with the PIB phase in the PDMAAm-1-PIB networks were higher than those of the reference homoPIBs which may be due to PIB chain-ends embedded in the glassy PDMAAm phase restricting segmental mobility. The Tg of the PIB phase in the PDMAAm-1-PIB increases by increasing the PIB content which may be due to an increase in crosslink density. In contrast, the Tg for the PDMAAm phase in the network decreases upon increasing the PIB content. Interaction of the (-CH2-CH-) moiety of the PDMAAm with the flexible PIB and thus the formation of a more flexible structure may explain this phenomenon.

Fig.49 Composition distribution dependence of reduced domain spacing, D/D0, of PS- -P2VP with single microphase-separated structure. Do = 60.8 nm is domain spacing of parent copolymer with Mn = 125 kg/mol. Hatched region macrophase separation. From [160], Copyright 2003 American Chemical Society...

Solid films of our block copolymers and their surface behavior have been examined using a variety of techniques. Block copolymers composed of incompatible polymer blocks are known for mesophase formation as a consequence of the microphase separation of the chains. Our fluorinated block copolymers form a microphase-separated structure with a high degree of order. This can easily be visualized by polarization microscopy and SAXS. 

Predicting the characteristic sizes and morphologies of these nanostructures has been an intense topic of investigation from both the theoretical and experimental points of view. Critical parameters are the degree of polymerization and the volume fraction of the constituent blocks, as well as the Flory-Huggins parameter between them. More complete information about microphase separated structures in bulk block copolymers can be found in the book of Hamley [2],... 

In addition to the previously mentioned driving forces that determine the bulk state phase behavior of block copolymers, two additional factors play a role in block copolymer thin films the surface/interface energies as well as the interplay between the film thickness t and the natural period, Lo, of the bulk microphase-separated structures [14,41,42], Due to these two additional factors, a very sophisticated picture has emerged from the various theoretical and experimental efforts that have been made in order to describe... 

In binary blends of A homopolymer and AB diblock copolymer, the interplay between microphase separation and macrophase separation is controlled mainly by the relative length of the chains, in addition to the composition of the mixture. Homopolymers shorter than the corresponding block tend to be solubilized within the corresponding domain of a microphase-separated structure. As the homopolymer molecular weight increases to approach that of the corresponding... 

Seguela and Prud homme (1989) investigated a PE-PEP-PE triblock copolymer containing 27wt% poly(ethylene) cast from a neutral solvent close to the Tm of PE and well below it. The samples cast above Tm crystallized within the assumed hexagonal-packed cylinder microphase-separated structure. However, SAXS experiments performed on the samples cast at room temperature suggested that crystallization occurred without prior microphase separation in the melt. This path dependence is a general feature of crystallization in block copolymers. 

UsingTEM to identify blend morphology, two diblocks with/ps 0.8 that form cubic-packed spherical phases and cylindrical phases respectively in the pure copolymer were found not to macrophase separate in a blend with d = 2.2, but to form single domain structures (cylinders or spheres) in the blend (Koizumi et al. 1994c). Similarly, blending a diblock with fK = 0.26 with one with fK = 0.64 (d = 1.2) led to uniform microphase-separated structures, with a lamellar phase induced in the 50 50 blend. Vilesov et al. (1994) also observed that blending two PS-PB diblocks with approximately inverse compositions (i.e. 22wt% PS and 72 wt% PS) induces a lamellar phase in the 50 50 blend. These examples all correspond to case (i). 

Micromechanical experiments made so far can be roughly divided into two parts (i) design of special techniques to measure and evaluate separately different contributions in the net force, such as adhesion, friction, deformation, and (ii) imaging of various heterogeneous surfaces such as blends, composites and microphase separated structures by conventional SFM s to collect statistical information and understand the origin of the mechanical contrast. Many of the micromechanical experiments were discussed elsewhere [58, 67, 68, 381, 412-414]. Here we will focus on recent advances in analytical applications of the active probe SFM. 

An interesting, but little-exploited, strategy is to use a regular thickness gradient created by patterned substrates in order to achieve complex sequenced microphase-separated structures within macroscopic topographic patterns [55, 56],... 

The increase of the solvent concentration in SB41 films on raising the partial pressure of chloroform vapor, and the related loss of long-range order, can be explained in terms of the so-called dilution approximation for the bulk block copolymer phases [167, 168], The above results clearly demonstrate the high sensitivity of the polymer-polymer interactions towards solvent content. Therefore, the microphase-separated structures in swollen block copolymer films can be used as a qualitative measure of the degree of swelling of the films [49, 166],... 

Figure 18c displays swelling kinetics of two SV films with the same initial thickness but different microphase-separated structures. The curves show up to 10% larger swelling (smaller poi) of SV films with the initial bulk lamella morphology as compared to the films with the non-bulk micelle phase [119],... 

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