Molecular insights on poly(N-isopropylacrylamide) coil-to-globule transition induced by pressure

By using extensive all-atom molecular dynamics simulations of an atactic linear polymer chain, we unveil the role of pressure in the coil-to-globule transition of poly(N-isopropylacrylamide) (PNIPAM).

Extremely tough cyclic peptide nanopolymers

ABSTRACTWe present a new class of bioinspired nanomaterials that are stabilized by a combination of covalent and hydrogen bonds. Prior work by others has shown that cyclic peptides can self-assemble to form supramolecular assemblies through backbone-backbone hydrogen bonding. To improve upon this molecular architecture, we develop a synthesis route to polymerize cyclic peptides and form a linear polymer chain that can transition between a rigid nanorod and an unfolded conformation. For a cyclic peptide polymer containing amine-terminated side chains on each ring, we demonstrate self-assembly can be triggered in aqueous solutions by varying the pH. We measure the elastic modulus of the rigid nanorods to be ca. 50 GPa, which is comparable to our molecular dynamics (MD) prediction (ca. 64 GPa). Our results highlight the uniqueness of our molecular architecture, namely their exemplary toughness (up to 3 GJ m-3), in comparison to other cyclic peptide-based assemblies. Finally, we demonstrate amphiphilic cyclic β-peptides are capable of inhibiting the growth of gram-negative and gram-positive bacteria.

Precise grafting of macrocyclics and dendrons to a linear polymer chain

Sequential growth of multifunctional telechelic polymer chains allowing grafting of polymeric dendrons and cyclics equally spaced along the backbone.

Computer Simulation Study on Solubility of Three-Dimensional Polymer Multiple Chain System

The author adopts Monte Carlo compute method to simulate the linear polymer chain lattice model in multiple chain systems of chain length n=20, 50, 100 while the volume fraction Φ=0.125, and makes a research on the variational situation of the solubility with changing of the interaction energy between solvent molecule and polymer chain segment molecule εPS. The results indicate, the solvent become not benefit to solve, the polymer chain turn into the ruleless coil shape, and the polymer groups overlap across with the increase of the interaction energy εPS.

Monte Carlo Simulation on Conformation Properties of Polymer Multiple Chain System

The author adopts Monte Carlo compute method to simulate the linear polymer chain lattice model in multiple chain systems of different volume fraction Φ while chain lengthn=50, and makes a research on the variational situation of the size (measured with the mean-square end-to-end distance <R2> and the mean-square radius of gyration <S2>), shape (measured with the mean asphericity factor ) with changing of the interaction energy between solvent molecule and polymer chain segment moleculeεPS. Results indicate <R2>, <S2> and have the changing rules that they become small with the increase of theεPS.

Computer Simulation on Conformation Properties of Polymer Chain

The author adopts Monte Carlo compute method to simulate the linear polymer chain lattice model in multiple chain systems of chain lengthn=20, 50, 100 while the volume fraction Φ=0.125, and makes a research on the variational situation of the size (measured with the mean-square end-to-end distance <R2> and the mean-square radius of gyration <S2>), shape (measured with the mean asphericity factor <A>) with changing of the interaction energy between solvent molecule and polymer chain segment molecule εPS. Results indicate <R2>, <S2> and <A> have the changing rules that they become small with the increase of the εPS

DEPENDENCE OF THE DAVYDOV'S SOLITON BEHAVIOR IN THE LINEAR POLYMER CHAIN ON THE EXCITON–PHONON COUPLING

The Davydov's soliton propagation in the linear polymer chain is analyzed numerically by solving the discrete equations of motion for exciton and phonon amplitudes. The main difference with respect to the results of continual approximation is that two exciton–phonon coupling constants influence separately the soliton behavior. Their influence is studied both in the ideal chain and the chain with single impurity.

Self-Oscillating Gel as Smart Materials

We have developed polymer and gels with an autonomous self-oscillating function by utilizing the Belousov-Zhabotinsky (BZ) reaction. Under the coexistence of the substrates, the polymer undergoes spontaneous cyclic soluble-insoluble changes or swelling-deswelling changes (in the case of gel) without any on-off switching of external stimuli. By using microfabrication technique, ciliary motion actuator or self-walking gel have been demonstrated. Further, in order to realize nano-actuator, the linear polymer chain and the submicrometer-sized gel beads were prepared. By grafting the polymers or arraying the gel beads on the surface of substrates, we have attempted to design self-oscillating surface as nano-conveyer. For application to biomaterials, it is necessary to cause the self-oscillation under biological condition without using non-biorelated BZ substrates. So we attempted to introduce pH-control site and oxidant-supplying site into the polymer. By using the polymer, self-oscillation only in the existence of biorelated organic acid was actually achieved.