The Largest Quasicrystalline Tiling with Dodecagonal Symmetry from a Single Pentablock Quarterpolymer of the AB1CB2D Type.

A quasicrystalline tiling pattern with tile size of ca. 60 nm has been discovered in the bulk state of a four-component pentablock polymer molecule of the AS1IS2P type, where A, S, I, and P denote poly(4-vinylbenzyldimethylamine), polystyrene, polyisoprene, and poly(2-vinylpyridine), respectively. The polymer samples used were prepared by anionic polymerizations and have narrow molecular weight distribution. The sample films were obtained by an extremely slow solvent-cast process from dilute solutions of tetrahydrofuran for 14 days. It has been found by TEM observation that the quarterpolymer, AS1IS2P-4 (Mn = 149 kg/mol, ϕA/ϕS1/ϕI/ϕS2/ϕP = 0.12/0.27/0.20/0.29/0.13), reveals two final stable structures, i.e., a 3.3.4.3.4 periodic tiling pattern as a minor component and a quasicrystalline (QC) tiling with dodecagonal symmetry as a major component, where the former includes a triangle/square number ratio of 2 and the latter has one of approximately 2.28, which is close enough to the ideal ratio, 4/ 3 ≑ 2.31, for the triangle/square random tiling of the dodecagonal QC tiling (DDQC). Two structures were also clearly proved by SAXS diffraction patterns. Here, it should be noted this QC structure having a tile side length of ca. 60 nm was created with a single block polymer molecule.

Hexagonally Packed Cylindrical Structures with Multiple Satellites from Pentablock Quarterpolymers of the AB1CB2D Type and Their Blends with Homopolymers.

Three kinds of hexagonally packed cylindrical (HPC) structures with 10/8 satellites have been found from a neat pentablock quarterpolymer of the AS1IS2P type, composed of poly(4-vinylbenzyldimethylamine) (A), polystyrene (S), polyisoprene (I), and poly(2-vinylpyridine) (P), and block polymer/homopolymer blends. AS1IS2P-2 (M = 276k, ϕA/ϕS1/ϕI/ϕS2/ϕP = 0.08/0.17/0.12/0.33/0.30) shows HPC of P with 10 single-arrayed I satellites and 6 A subsatellites in the S matrix, where the I/P ratio number is 5, while AS1IS2P-2 (M = 325k, ϕA/ϕS1/ϕI/ϕS2/ϕP = 0.07/0.31/0.14/0.18/0.30)/Sh(M;11k) = 90/10 blend reveals another HPC of P with 10 I satellites, giving an I/P ratio of 6, whose array of I is a single/double mixture. Moreover, AS1IS2P-1/Sh/Ah(M;9k) = 90/5/5 blend represents two enantiomeric HPC packings with 8 double-arrayed I satellites having an I/P ratio of 7, which can be considered to be approximants of two enantiomeric 3.3.3.3.6 Archimedean tilings. These structures were conceived to be formed by the enhanced miscibility of tail A-chains with added homopolymers, resulting in an increase of the (A + S)/I interaction leading to the split of I domains.

Triply Helical Giant Domain with Homochirality in a Terpolymer Blend System.

Hexagonally packed coaxial triply helical domains with a mesoscopic length scale in matrices were created from an S1IS2P tetrablock terpolymer/Sh homopolymer blend system, wherein S1, S2, and Sh denote polystyrene, I is polyisoprene, and P represents poly(2-vinylpyridine). Two terpolymers, i.e., S1IS2P-3 (S1/I/S2/P = 0.50/0.17/0.19/0.14, M = 134k) and S1IS2P-4 (S1/I/S2/P = 0.58/0.16/0.10/0.16, M = 173k), were blended with Sh (M = 3k) at various concentrations. In the S1IS2P-3/Sh = 80/20 blend, the helical domain of P (o.d.= 19 nm; h.p. = 34 nm) was displayed by TEM, and the helical I phase (o.d. = 55 nm; i.d. = 29 nm; h.p. = 34 nm) was clearly demonstrated by 3D-TEM tomography. Essentially the same structure was confirmed to be created from the S1IS2P-4/Sh blend. These findings point out that S2 chains fill the gap between the I and P helices, and hence the intermediate S phase also has a helical nature. Moreover, it is worth noting that grains composed of hexagonally packed helices reveal homochirality.

Acidity effects of medium fluids on anhydrous proton conductivity of acid-swollen block polymer electrolyte membranes.

Proton-conductive polymer electrolyte membranes (PEMs) were prepared by infiltrating sulfuric acid (Sa) or phosphoric acid (Pa) into a polystyrene-b-poly(4-vinylpyridine)-b-polystyrene (S-P-S) triblock copolymer. When the molar ratio of acid to pyridyl groups in S-P-S, i.e., the acid doping level (ADL), is below unity, the P-block/acid phase in the PEMs exhibited a moderately high glass transition temperature (T g) of ∼140 °C because of consumption of acids for forming the acid-base complexes between the pyridyl groups and the acids, also resulting in almost no free protons in the PEMs; therefore, the PEMs were totally glassy and exhibited almost no anhydrous conductivity. In contrast, when ADL is larger than unity, the T gs of the phase composed of acid and P blocks were lower than room temperature, due to the excessive molar amount of acid serving as a plasticizer. Such swollen PEMs with excessive amounts of acid releasing free protons were soft and exhibited high conductivities even without humidification. In particular, an S-P-S/Sa membrane with ADL of 4.6 exhibited a very high anhydrous conductivity of 1.4 × 10-1 S cm-1 at 95 °C, which is comparable to that of humidified Nafion membranes. Furthermore, S-P-S/Sa membranes with lower T gs exhibited higher conductivities than S-P-S/Pa membranes, whereas the temperature dependence of the conductivities for S-P-S/Pa is stronger than that for S-P-S/Sa, suggesting Pa with a lower acidity would not be effectively dissociated into a dihydrogen phosphate anion and a free proton in the PEMs at lower temperatures.

Melt rheology of tadpole-shaped polystyrenes with different ring sizes.

In this study, linear melt rheology of a single-tail tadpole-shaped polystyrene, ST-30/80, having ring and linear sizes of MR ∼ 30 kg mol-1 and ML ∼ 80 kg mol-1, respectively, was examined, and the effect of the ring size on rheological properties of tadpole polymers was discussed by comparing with the data of the previously reported tadpole samples having MR ∼ 60 kg mol-1. ST-30/80 exhibits an entanglement plateau and shows a clearly slower terminal relaxation than that of its component ring and linear polymers. When the zero-shear viscosity η0 for ST-30/80 is plotted against the molecular weight of a linear tail chain, the data point lies on the single curve of η0 for 4- and 6-arm star polymers and the single-tail tadpoles with MR ∼ 60 kg mol-1. These results suggest that the tadpole molecule in this study spontaneously forms a characteristic entanglement network, i.e., the intermolecular ring-linear threading, in the same manner as the previous tadpole samples, even though the size of the ring part is just slightly larger than the entanglement molecular weight (i.e., MR ∼ 1.8Me).

Periodic and Aperiodic Tiling Patterns from a Tetrablock Terpolymer System of the A1BA2C Type.

Two tetrablock terpolymers of the S1IS2P type, where S, I, and P denote polystyrene, polyisoprene, and poly(2-vinylpyridine), respectively, were prepared anionically. S1IS2P-1 (S1/I/S2/P = 0.35/0.16/0.34/0.15, four numbers being volume fractions of S1, I, S2, and P block chains) has a structure with double hexagonal cylinders, while S1IS2P-2 (S1/I/S2/P = 0.47/0.15/0.22/0.16) has an unusual double tetragonal structure. Moreover, 13 binary blends were prepared from these two parent polymers. Among them, five blends with α(= φS1/φS2) covering the range 1.50 ≤ α ≤ 1.86 were confirmed to have a 3.3.4.3.4 Archimedean tiling structure, in which their P domains adopt five satellite I domains, while four blends with α covering the range 1.37 ≤ α ≤ 1.48 were revealed to be a quasicrystalline tiling structure with dodecagonal symmetry.

Dimensions of catenated ring polymers in dilute solution studied by Monte-Carlo simulation.

Interaction between two simple ring chains catenated in a molecule was estimated by a Metropolis Monte Carlo simulation, and the result was compared with a model. We employed catenated ring chains in this study; they were composed of two simple ring chains, and the topology was kept as 2 1 2 . The temperature dependence of the distance between two ring chains in a molecule was discussed using Flory's scaling exponent, ν, in R g ∝ N ν , where R g is the radius of gyration of a simple ring chain catenated in a molecule. In the simulation, the topology of the component rings and their links were kept because chain crossing was prohibited. The excluded volume of chains was screened by the attractive force between polymer segments, and the strength of the attractive force depends on temperature, T. At the θ temperature for trivial ring polymers, where the condition ν = 1/2 holds, their trajectories can be described statistically as a closed-random walk, i.e., a closed-phantom chain model. The temperature at which interaction between trivial ring polymers, i.e., inter-molecular interaction, is repulsive; trivial ring polymer molecules show the excluded volume generated with keeping their own topology, 01. A catenated molecule is composed of two simple rings, and so forth a component ring can be affected by the existence of the counterpart rings. Under that temperature, the mean-square distance between two rings in a catenated molecule, ⟨L 2⟩, was obtained and compared with that of the simple model composed of two circles in three-dimensions, where interaction between circles is set as zero. It has been found that the simulated ⟨L 2⟩ values were constantly larger than those of the model owing to the excluded volume of rings in a molecule.

Thin Films with Perpendicular Tetragonally Packed Rectangular Rods Obtained from Blends of Linear ABC Block Terpolymers.

A binary blend of poly(isoprene-block-styrene-block-(2-vinylpyridine)) (ISP) triblock terpolymers, having the same chain length but different compositions, was used to achieve an ordered lattice with 4-fold symmetry of rectangular-shaped rods of poly(isoprene) (I) and poly(2-vinylpyridine) (P). In given conditions, the I and P domains were oriented perpendicularly to the substrate, providing an appealing type of templates for nanopatterning. Thin films were prepared by spin coating, exposed to solvent vapor (providing morphological reorganization), and then characterized by atomic force microscopy, transmission electron microscopy, and grazing-incidence small-angle X-ray scattering. Selective I and P identifications were carried out by AFM and TEM on a model ISP, as well as development of a technique of electronic contrast enhancement to better assign the self-assembly structure in GISAXS.

Morphology of symmetric ABCD tetrablock quaterpolymers studied by Monte Carlo simulation.

Morphology of symmetric ABCD tetrablock quaterpolymers in melt was studied by the Monte Carlo (MC) simulation, where the volume fractions of the block chains, f, kept the relationships of fA=fD and fB=fC, and the volume fraction of the two mid-blocks φ was defined as φ=fB+fC. Previous self-consistent field theory for ABCD reported morphological change including several structures; however, the scope was limited within a two-dimensional system. To the contrary, in this paper, MC simulations were carried out in three dimensions with changing the φ value finely, which resulted in finding a tetracontinuous structure in the range of 0.625≤φ≤0.75. Moreover the tetracontinuous structure has been found to be the gyroid structure, and the mean curvature of the B/C interface is nearly zero. We concluded that the B/C interface must be the Schoen gyroid surface, one of three-dimensional periodic minimal surfaces. The geometrical nature of the A/B interface should be equivalent to that of the C/D interface, and they stand as level surfaces to the Schoen gyroid surface.

Highly Extensible Supramolecular Elastomers with Large Stress Generation Capability Originating from Multiple Hydrogen Bonds on the Long Soft Network Strands.

Highly extensible supramolecular elastomers are prepared from ABA triblock-type copolymers bearing glassy end blocks and a long soft middle block with multiple hydrogen bonds. The copolymer used is polystyrene-b-[poly(butyl acrylate)-co-polyacrylamide]-b-polystyrene (S-Ba-S), which is synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization. Tensile tests reveal that the breaking elongation (εb ) increases with an increase in the middle block molecular weight (Mmiddle ). Especially, the largest S-Ba-S with Mmiddle of 3140k, which is synthesized via high-pressure RAFT polymerization, achieves εb of over 2000% with a maximum tensile stress of 3.6 MPa, while the control sample without any middle block hydrogen bonds, polystyrene-b-poly(butyl acrylate)-b-polystyrene with Mmiddle of 2780k, is merely a viscous material due to the large volume fraction of soft block. Thus, incorporation of hydrogen bonds into the large molecular weight soft middle block is found to be beneficial to prepare supramolecular elastomers attaining high extensibility and sufficiently large stress generation ability simultaneously. This outcome is probably due to concerted combination of entropic changes and internal potential energy changes originating from the dissociation of multiple hydrogen bonds by elongation.

Interactions between ring polymers in dilute solution studied by Monte Carlo simulation.

The second virial coefficient, A2, for trivial-ring polymers in dilute condition was estimated from a Metropolis Monte Carlo (MC) simulation, and the temperature dependence of A2 has been discussed with their Flory's scaling exponent, ν, in Rg ∝ N(ν), where Rg is radius of gyration of a polymer molecule. A limited but not too small number of polymer molecules were employed in the simulation, and the A2 values at various temperatures were calculated from the molecular density fluctuation in the solution. In the simulation, the topology of ring polymers was kept, since chain crossing was prohibited. The excluded volume effects can be screened by the attractive force between segments, which depends on the temperature, Tα, defined in the Metropolis MC method. Linear and trivial-ring polymers have the ν value of 1/2 at Tα = 10.605 and 10.504. At Tα = 10.504, the excluded volume effects are screened by the attractive force generated between segments in a ring polymer, but the A2 value for ring polymers is positive. Thus, the temperature at A2 = 0 for a ring polymer is lower than that at ν = 1/2, and this fact can be explained with the following two reasons. (a) Rg value for a ring polymer is much smaller than that for a linear polymer at the same temperature and molecular weight, where interpenetration of a ring polymer chain into neighboring chains is apparently less than a linear chain. (b) The conformation of trivial rings can be statistically described as a closed random walk at ν = 1/2, but their topologies are kept, being produced topological constraints, which strongly relate not only to the long-distance interaction between segments in a molecule but also the inter-molecular interaction.

Formation of Tetragonally-Packed Rectangular Cylinders from ABC Block Terpolymer Blends.

Effect of composition distribution of ABC linear terpolymers on the formation of periodic structures was investigated. Five poly(isoprene-b-styrene-b-2-vinylpyridine) (ISP) triblock terpolymers with almost constant molecular weights of ca. 130k and with similar center-block fraction at around 0.55, were blended variously. It has been found that tricontinuous gyroid structures gradually transform into a cylindrical structure whose rectangular cylinders are packed tetragonally if composition distribution increases. Further experiments by 3D-TEM observation on binary equimolar mixtures of two molecules with similar molecular weights of 122k and 124k, giving the average composition of φI/φS/φP = 0.23/0.59/0.18, has verified to show more evident rectangular-shaped cylinders with 4-fold symmetry. This new structure, having periodic surfaces with nonconstant mean-curvature, could be formed due to the systematic localization of component polymer chains along the domain interfaces.

Chain conformations of ring polymers under theta conditions studied by Monte Carlo simulation.

We studied equilibrium conformations of trivial-, 31-knot, and 51-knot ring polymers with finite chain length at their θ-conditions using a Monte Carlo simulation. The polymer chains treated in this study were composed of beads and bonds on a face-centered-cubic lattice respecting the excluded volume. The Flory's critical exponent ν in Rg ~ N(ν) relationship was obtained from the dependence of the radius of gyration, Rg, on the segment number of polymers, N. In this study, the temperatures at which ν equal 1∕2 are defined as θ-temperatures of several ring molecules. The θ-temperatures for trivial-, 31-knot, and 51-knot ring polymers are lower than that for a linear polymer in N ≤ 4096, where their topologies are fixed by their excluded volumes. The radial distribution functions of the segments in each molecule are obtained at their θ-temperatures. The functions of linear- and trivial-ring polymers have been found to be expressed by those of Gaussian and closed-Gaussian chains, respectively. At the θ-conditions, the excluded volumes of chains and the topological-constraints of trivial-ring polymers can be apparently screened by the attractive force between segments, and the values for trivial ring polymers are larger than the half of those for linear polymers. In the finite N region the topological-constraints of 31- and 51-knot rings are stronger than that of trivial-ring, and trajectories of the knotted ring polymers cannot be described as a closed Gaussian even though they are under θ-conditions.

Anisotropic self-assembly of gold nanoparticle grafted with polyisoprene and polystyrene having symmetric polymer composition.

Methodology to self-assemble metal nanoparticles into three-dimensional mesoscale patterns is a fundamental technique to construct functional materials. Here, we demonstrate that hybridizing an immiscible polymer pair with a metal nanoparticle allows the hybrid to self-assemble in the film, resulting in spontaneous alignment of the nanoparticles at the phase-separated interface formed by the constituent polymers. Organic-inorganic hybrids composed of polyisoprene, polystyrene, and gold nanoparticle were prepared by multistep "grafting-to" method coupled with alkyne-azide click reaction. The polymer composition can be controlled by the feed ratio of gold nanoparticle to azide ligands. The gold nanoparticle hybrid with symmetric polymer composition forms an "alternating lamellar" structure of polyisoprene and polystyrene, where the gold nanoparticles were forced into the phase-separated interfaces.

Topological constraint in ring polymers under theta conditions studied by Monte Carlo simulation.

We studied equilibrium conformations of trivial-, 3(1)-, and 5(1)-knotted ring polymers together with a linear counterpart over the wide range of segment numbers, N, from 32 up through 2048 using a Monte Carlo simulation to obtain the dependence of the radius of gyration of these simulated polymer chains, R(g), on the number of segments, N. The polymer chains treated in this study are composed of beads and bonds placed on a face-centered-cubic lattice respecting the excluded volume. The Flory's critical exponent, ν, for a linear polymer is 1/2 at the θ-temperature, where the excluded volume is screened by the attractive force generated among polymer segments. The trajectories of linear polymers at the θ-condition were confirmed to be described by the Gaussian chain, while the ν values for trivial-, 3(1)-, and 5(1)-knots at the θ-temperature of a linear polymer are larger than that for a linear chain. This ν value increase is due to the constraint of preserving ring topology because the polymer chains dealt with in this study cannot cross themselves even though they are at the θ-condition. The expansion parameter, ß, where N-dependence vanishes by the definition, for trivial-, 3(1)-, and 5(1)-knotted ring polymers is obtained at the condition of ν = 1/2. It has been found that ß decreases with increasing the degree of the topological constraint in the order of trivial (0.526), 3(1) (0.422), and 5(1) knot (0.354). Since the reference ß value for a random knot is 0.5, the trivial ring polymer is swollen at ν = 1/2 and the other knotted ring polymers are squeezed.

Fabrication and modification of ordered nanoporous structures from nanophase-separated block copolymer/metal salt hybrids.

We report facile preparation of nanoporous thin films by rinsing out a metal salt from nanophase-separated hybrid films composed of a block copolymer and a water-soluble metal salt. Nanophase-separated hybrids were prepared by mixing polystyrene-b-poly(4-vinylpyridine) (PS-P4VP) and iron(III) chloride in a solvent of pyridine, followed by solvent-casting and thermal-annealing. Film samples with a thickness of ca. 100 nm were fabricated from the nanophase-separated hybrids by using a microtoming technique. Metal salts in the films were removed by immersion into water to fabricate nanopores. Morphological observations were conducted by using transmission electron microscopy (TEM). Ordered cylindrical nanopores were clearly observed in the thin films prepared from the water-immersed hybrids which originally present cylindrical nanodomains. These nanoporous films were modified by loading another metal salt, samarium(III) nitrate, into the nanopores on the basis of the coordination ability of P4VP tethered to the pore walls. The samples after loading treatment were evaluated by TEM observation and elemental analysis with energy dispersive X-ray spectroscopy.

The theta-temperature depression caused by topological effect in ring polymers studied by Monte Carlo simulation.

We studied equilibrium conformations of linear and ring polymers in dilute solutions over the wide range of segment number N of up to 2048 with Monte Carlo simulation, and evaluated N dependence of the radii of gyration, R(g), of chains. The polymer molecules treated in this study are assumed to be composed of beads and bonds, and they are put in a three-dimensional face-centered cubic (FCC) lattice. The values of Flory's critical exponent, ν, for linear and ring polymers were estimated from the N dependence of R(g), and the temperatures at which ν reach 1/2 were obtained. Here we define those as Θ-temperatures in this report. The simulation result shows that the Θ-temperature for ring polymers is evidently lower than that of the linear polymers, and the origin of the Θ-temperature depression is discussed. Since R(g) of a ring polymer is smaller than that for a linear polymer at the same N and temperature, the segment density for a ring polymer is increased by the topological effect and the repulsive force between segments of a ring polymer at the Θ-temperature for a linear polymer is stronger. Thus, the origin of the Θ-temperature depression for ring polymers is the repulsive force emphasized by the topological effect of rings.

Kaleidoscopic morphologies from ABC star-shaped terpolymers.

Star-shaped terpolymers of the ABC type composed of incompatible polymer components give a variety of ordered structures with mesoscopic length scales depending on their composition ratio. Their peculiar features are summarized in this report. Polymer components adopted are polyisoprene (I), polystyrene (S) and poly(2-vinylpyridine) (P), and many monodisperse samples of the I(X)S(Y)P(Z) type were anionically prepared. Firstly our focus is on molecules of the I(1.0)S(1.0)P(x(1)) type, where x(1) is only a variable. The complex but systematic morphology change was displayed within the range 0.2 ≤ x(1) ≤ 10, that is, their structures change from spherical plus lamellae structure for I(1.0)S(1.0)P(0.2) to periodic tilings (0.4 ≤ x(1) ≤ 1.9), then to lamellae-in-lamella (3.0 ≤ x(1) ≤ 4.9) and lamellae-in-cylinder (7.9 ≤ x(1) ≤ 10) structures with increasing x(1). Here if we pay attention to the structural variation of the P domain inclusively, it transforms from sphere to cylinder, lamella and then to matrix, which is the same as that for linear polymers. Among them, several periodic Archimedean tiling patterns can be naturally formed when the relative lengths of the three chains are close to one another. Moreover, it has been found that the tiling zone is spread out widely. For example, the series I(1.0)S(1.8)P(x(2)) (with 0.8 ≤ x(2) ≤ 2.9) and the other series I(1.0)S(y)P(2.0) (with 1.1 ≤ y ≤ 2.7) show mostly Archimedean tilings. Additionally, block copolymer/homopolymer blends with a composition of I(1.0)S(2.7)P(2.5) reveal a quasicrystalline tiling with dodecagonal symmetry. Furthermore, a zinc-blende-type four-branched network structure was created just a little outside of the tiling region for a block copolymer/homopolymer blend of I(1.0)S(2.3)P(0.8). When some more asymmetry in chain length is introduced, hyperbolic tiling on a gyroid membrane has successfully been constructed for the sample I(1.0)S(1.8)P(3.2) and it transforms into a hierarchical cylinders-in-lamella structure with further increase in P content to I(1.0)S(1.8)P(6.4). Thus, kaleidoscopic morphologies have been generated from ABC star-shaped terpolymers and their structural change has turned out to be very sensitive to relative compositions.

Formation of undulated lamellar structure from ABC block terpolymer blends with different chain lengths.

The effect of molecular weight distribution of ABC linear terpolymers on the formation of periodic structures was investigated. Three poly(isoprene-b-styrene-b-2-vinylpridine) triblockterpolymers with molecular weights of 26k, 96k, and 150k were blended variously. Three-phase, four-layer lamellar structures were observed when polydispersity index (PDI) was low, but it has been found that simple lamellar structure with flat surface transforms into an undulated lamellar one, where two interfaces, i.e., I/S and S/P, are both undulated, and they are synchronizing each other if PDI exceeds the critical value. This new structure could be formed due to the periodic and "weak" localization of three chains along the domain interfaces, which produces periodic surfaces with nonconstant mean curvatures. With further increase of PDI, the blend macroscopically phase-separated into different microphase-separated structures.

Shape-directed assembly of a "macromolecular barb" into nanofibers: stereospecific cyclopolymerization of isopropylidene diallylmalonate.

Cyclopolymerization of isopropylidene diallylmalonate (1) in CH(2)Cl(2) using as the initiator a crystallographically defined alpha-diimine Pd(II) complex with a trans-azobenzene strap (trans-3) proceeds stereospecifically to give a cycloolefinic polymer that is rich in threo-disyndiotactic sequences (st(rich)-2; syndiotactic tetrad content = 60% at -10 to 0 degrees C). Polymer 2, when perfectly threo-disyndiotactic, adopts a "barb"-shaped geometry with its cyclic malonate pendants sticking out alternately up and down along the rigid main chain. Under appropriate conditions, st(rich)-2 regularly self-assembles, not only in the solid state but also in solution, into nanofibers that eventually give rise to physical gelation of halogenated solvents such as CH(2)Cl(2). In sharp contrast, a reference polymer 2 that is rich in threo-diisotactic sequences (it(rich)-2), which likely adopts a helical geometry, has poor self-assembly capability in solution and neither forms nanofibers nor induces physical gelation of CH(2)Cl(2).