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75th annual meeting of the Japanese Society of Microscopy, June 17–19, 2019, Nagoya, Japan

A series of well-defined titanium-containing random, diblock, and triblock copolymers were prepared by ruthenium-catalyzed living radical polymerization of glycidyl methacrylate followed by amination of the epoxy group with diethanolamine and titanium complex loading, which was achieved by reacting the resulting triethanolamine pendent group with CpTiCl3 or Cp*TiCl3 (Cp: cyclopentadienyl; Cp*: pentamethylcyclopentadienyl). The titanium-containing unit obtained by this procedure possessed a discrete atrane structure, which contributed to the formation of soluble well-defined polymers without cross-linking via uncontrolled intermolecular multisite ligation to the titanium center. In addition, the Cp* derivatives were highly stable to moisture. The same strategy was used successfully to construct well-defined titanium end-functionalized polymers, and an epoxy-functionalized initiator was used in the ruthenium-catalyzed living radical polymerization of methyl methacrylate, followed by postreactions with dieth...

A microphase-separated structure of a poly(deuterated styrene-block-2-vinylpyridine) (dPS-b-P2VP) block copolymer thin film was studied by neutron reflectivity (NR). The spun-coated dPS-b-P2VP block copolymer (on a Si substrate) showed the coexistence of a minority thin lamellar layer (holes) dispersed in a majority thick layer. The “terraced structure” was formed due to the mismatch between the initial film thickness and the intrinsic lamellar periodicity of the dPS-b-P2VP block copolymer. The amount and height of the holes were evaluated using atomic force microscopy (AFM), transmission electron microscopy (TEM) and transmission electron microtomography (TEMT). The three-dimensional (3D) images obtained from the TEMT experiments clearly showed that the microphase-separated structure inside the thin film was homeotropically aligned. The thickness of the thick and the thin lamellar layers corresponded to (5/2)L0 and (3/2)L0, respectively (L0 is the lamella periodicity in the bulk state). The NR profile from the dPS-b-P2VP thin film, Rexp, showed many distinctive scattering peaks. Based on the structural information obtained from the microscopy, a scattering length density profile along the depth direction, i.e., the direction normal to the film surface, b/vTEMT, was evaluated, which was then used as an initial profile in the conventional model fitting method. An excellent best-fit to Rexp was obtained using b/vTEMT, even though the thin film had the terraced structure. The surface coverage of the holes was estimated from the resulting b/v, which was in good agreement with the estimated value from TEM.

Ruthenium-catalyzed living radical polymerization was applied to the synthesis of a series of all methacrylic well-defined AxBAx-type block−graft copolymers consisting of soft middle segments [dodecyl methacrylate (DMA)] and hard outer graft chains [methyl methacrylate (MMA)] with controlled lengths of the backbone and graft chains and controlled graft numbers. This synthetic method was based on the CHCl2(COPh)/Ru(Ind)Cl(PPh3)2-initiated sequential living radical block copolymerization of DMA and 2-(trimethylsilyoxy)ethyl methacrylate (TMSHEMA) followed by the direct transformation of the silyloxy groups into the ester with C−Br bond by 2-bromoisobutyroyl bromide and the ruthenium-catalyzed “grafting-from” polymerization of MMA. A series of the block−graft copolymers were then characterized by NMR, size-exclusion chromatography (SEC), multiangle laser light scattering (MALLS), differential scanning calorimetry (DSC), dynamic viscoelasticity, transmission electron microscopy (TEM), and atomic force microsc...

Novel copolymers with controlled architectures can function as new building blocks for well-defined nanostructures on the basis of microphase separation, unlike conventional ABA triblock copolymers. A series of well-defined A(x)BA(x)-type block-graft copolymers consisting of soft middle segments (dodecyl methacrylate (DMA)) and hard outer graft chains (styrene (St)) were synthesized by ruthenium-catalyzed living radical block and graft polymerization. NMR spectroscopy and size-exclusion chromatography combined with multiangle laser light scattering confirmed the well-defined structure of the A(x)BA(x) block-graft copolymers with backbones and graft chains of controlled lengths. Transmission electron microscopy and transmission electron microtomography revealed a series of morphologies for the copolymers. Morphological changes were observed from PSt "honeycomb" cylinders to lamellae and poly(DMA) cylinders with increasing PSt-graft content, whereby the phase diagram was shifted significantly to lower volume fractions of the larger-number component (St) relative to those of the corresponding ABA triblock copolymers. More specifically, poly(DMA) cylinders were observed even before the St content reached 50 wt %. The A(x)BA(x) and ABA copolymers with 17-30 wt % of St exhibited characteristics of a thermoplastic elastomer with tensile strengths of 1-6 MPa and elongations at break of 70-300 %. These mechanical properties can be related well to the microphase structures of the A(x)BA(x) and ABA copolymers.

ABC triblock copolymers are known to exhibit a wide variety of unique types of morphologies compared to AB diblock copolymers. In the present study, poly(styrene-block-(ethylene-alt-propylene)-block-(methyl methacrylate)) (SEPM) triblock copolymers were synthesized and their morphologies were extensively studied by transmission electron microtomography (TEMT). In the SEPM triblock copolymer, two kinds of morphologies coexist: One was the well-known knitting morphology, and the other was a novel morphology called the ladder morphology. The ladder morphology was a major morphology in the SEPM copolymer, the stability of which was discussed in terms of the interfacial area and the solubility parameters between the three components.