Coherent crystal branches: the impact of tetragonal symmetry on the 2D confined polymer nanostructure.

The symmetry of polymer crystals greatly affects the optical, thermal con-ductivity and mechanical properties of the materials. Past studies have shown that the two-dimensional (2D) confined crystallization of polymer nanorods could produce anisotropic structures. However, few researchers have focused on understanding confined nanostructures from the perspective of crystal sym-metry. In this research, we demonstrate the molecular chain self-assembly of tetragonal crystals under cylindrical confinement. We specifically selected poly(4-methyl-1-pentene) (P4MP1) with a 41 or 72 helical conformation (usually crystallizing with a tetragonal lattice) as the model polymer. We found a coherent crystal branching of the tetragonal crystal in the P4MP1 nanorods. The unusual 45°- and 135°-{200} diffractions and the meridional 220 diffraction (from 45°-tilted crystals) have shown a uniform crystal branching between the a 1-axis crystals and the 45°-tilted crystals in the rod long axis, which originates from a structural defect associated with tetragonal symmetry. Surprisingly, this chain packing defect in the tetragonal cell can be controlled to develop along the rod long axis in 2D confinement.

Magnifying the Structural Components of Biomembranes: A Prototype for the Study of the Self-Assembly of Giant Lipids.

How biomembranes are self-organized to perform their functions remains a pivotal issue in biological and chemical science. Understanding the self-assembly principles of lipid-like molecules hence becomes crucial. Herein, we report the mesostructural evolution of amphiphilic sphere-rod conjugates (giant lipids), and study the roles of geometric parameters (head-tail ratio and cross-sectional area) during this course. As a prototype system, giant lipids resemble natural lipidic molecules by capturing their essential features. The self-assembly behavior of two categories of giant lipids (I-shape and T-shape, a total of 8 molecules) is demonstrated. A rich variety of mesostructures is constructed in solution state and their molecular packing models are rationally understood. Giant lipids recast the phase behavior of natural lipids to a certain degree and the abundant self-assembled morphologies reveal distinct physiochemical behaviors when geometric parameters deviate from natural analogues.

Sequence isomeric giant surfactants with distinct self-assembly behaviors in solution.

We have designed and synthesized a pair of sequence isomeric giant surfactants based on polystyrene (PS) and polyhedral oligomeric silsesquioxane (POSS) nanoparticles. Although these two macromolecules possess identical compositions as "sequence isomers", the distinctly arranged POSS sequences lead to different molecular packing conformations, and further induce distinguished self-assembly behaviors in DMF/water solutions.

Multilevel Manipulation of Supramolecular Structures of Giant Molecules via Macromolecular Composition and Sequence.

We have successfully synthesized a series of monodispersed chain-like giant molecules with precisely controlled macromolecular composition and sequence based on polyhedral oligomeric silsesquioxane (POSS) nanoparticles using an orthogonal "click" strategy. Their nonspherical supramolecular structures, such as lamellae, double gyroids, and hexagonal packed cylinders, are mainly determined by the composition (namely, the number of incorporated amphiphilic nanoparticles). In addition, by precisely alternating the sequence of arranged nanoparticles in the giant molecules with identical chemical compositions, the domain sizes of their supramolecular structures could be fine-tuned. This is attributed to the macromolecular conformational differences caused by collective hydrogen bonding interactions in each set of sequence isomeric giant molecules. This work has demonstrated multilevel manipulation of supramolecular structures of giant molecules: coarse tuning by composition and fine-tuning by sequence.

A well-defined, versatile photoinitiator (salen)Co-CO2CH3 for visible light-initiated living/controlled radical polymerization.

The control of the polymerization of a wide range of monomers under mild conditions by a single catalyst remains a major challenge in polymer science. We report a versatile, well-defined organocobalt salen complex to control living radical polymerization of different categories of monomers, including acrylates, acrylamides and vinyl acetate, under visible light irradiation at ambient temperature. Both household light and sunlight were effectively applied in the synthesis of polymers with controlled molecular weights and narrow polydispersities. Narrowly dispersed block copolymers (Mw/Mn < 1.2) were obtained under various conditions. The structures of the polymers were analyzed by 1H NMR, 2D NMR, 13C NMR, GPC, MALDI-TOF-MS and isotopic labeling experiments, which showed that the ω and α ends of the polymer chains were capped with (salen)Co and -CO2CH3 segments, respectively, from the photoinitiator (salen)Co-CO2CH3. The ω end was easily functionalized through oxygen insertion followed by hydrolysis from 18O2 to -18OH. This robust system can proceed without any additives, and offers a versatile and green way to produce well-defined homo and block copolymers.