Superparticles Formed by Amphiphilic Tadpole-like Single Chain Polymeric Nanoparticles and Their Application as an Ultrasonic Responsive Drug Carrier

Herein, we report self-assembly of tadpole-like single chain polymeric nanoparticles （TPPs） and the ultrasonic response of the resultant superparticles. The TPPs are with an intramolecularly crosslinked poly（2-（methacryloyloxy）ethyl pent-4-ynoate）-rpoly（hydroxyethyl methacrylate） （PMAEP-r-PHEMA） chain as the ＂head＂ and a poly（2- （dimethylamino）ethyl methacrylate （PDMAEMA） linear chain as the ＂tail＂, and are pre- pared simply and emciently by Glaser-coupling of the pendant alkynes in the PMAEP-r- PHEMA block in the common solvent methanol. The formation of the TPPs was confirmed by gel permeation chromatograph, nuclear magnetic resonance spectroscopy, dynamic light scattering, static dynamic scattering, and transmission electron microscopy. In aqueous solution, the amphiphilic TPPs could self-assemble into regular superparticles, driven by aggregation of the hydrophobic ＂heads＂. Since in the structure there is no chain entanglement and the embedding of PDMAEMA chains disturb close-packing of the ＂heads＂, the superpartieles are responsive to a low-energy ultrasonic vibration, as evidenced by greatly enhanced release of the functional molecules from the superparticles by treatment of a low-energy ultrasound. Therefore, the superparticles should be very promising in the use as the drug carriers that can be manipulated from a long distance, considering that ultrasonic energy can be focused at a small area in a relatively long distance from the ultrasound-radiating source.

Structure of the Heterobimetallic Linear-Chain Polymeric Complex [NH_4]_n [WAgS_4]_n and Influence of Cationic Valence State on Configurations of Polymeric W/Ag/S Complexes

The title complex [NH4]n [WAgS4]n crystallizes in the tetragonalspace group I4 with crystallographic parameters: a = b = 7. 994 (2 ), c = 5. 855 (2 ):A,V = 373. g(2) A3, Z=2, Dc= 3. 89 g/cm3, F(000) = 392, μ= 19. 27 mm-l , A(MoKα) = 0. 71069, Mr = 438. 01, and the convergence factors R = 0. 045, Rw =0. 055 for 341 observed reflections (I>3σ(I)). The anion structure can be viewed as apolymeric single chain consisting of unlimited extended rhombic fragruents of -AgS2W-which are alternately perpendicular to each other. Additionally, influence of di- and tri-valent complex cations on the assembIy of WS2-4 and Ag+ is briefly discussed.

Synthesis of Branched Polyethylene via Bulky α-Diimine Nickel(II)-Catalyzed Ethylene Chain-Walking Polymerization

The catalysis of olefin polymerization through the chain-walking process is a subject of great interest. In this contribution, the successful synthesis of a Brookhart-type unsymmetrical α-diimine nickel catalyst Ni, which contains both dibenzhydryl and phenyl groups, was determined by X-ray crystallography. The compound has a pseudo-tetrahedral geometry at the Ni center, showing pseudo-C2-symmetry. Upon activation with modified methylaluminoxane (MMAO), Ni1 exhibits high catalytic activity up to 1.02 × 107 g PE (mol Ni h)−1 toward ethylene polymerization, enabling the synthesis of high molecular weight branched polyethylene. The molecular weights and branching densities could be tuned over a very wide range. The polymerization results indicated the possibility of precise microstructure control, depending on the polymerization temperature. The branching densities were decreased with increasing the polymerization temperature.

Evaluation of the clenbuterol imprinted monolithic column prepared by reversible addition-fragmentation chain transfer polymerization

To make more homogenous organic monolithic structure, reversible addition-fragmentation chain transfer （RAFT） process was employed in the synthesis of the clenbuterol imprinted polymer. In the synthesis, the influence of synthetic conditions on the polymer structure and separation efficiency was studied. The result demonstrated that the imprinted columns prepared with RAFT process have higher column efficiency and selectivity than the columns prepared with conventional polymerization in the present study, which may result from the higher surface area, smaller pore size and the narrower globule size distribution in their structures. The result indicated that RAFT polymerization provided better conditions for the clenbuterol imprinted monolithic polymer preparation. 2009 Xiang Chao Dong. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

SHAPE OF POLYMER CHAINS ON A TETRAHEDRAL LATTICE

The shape of unperturbed polymer chains was studied using the Monte Carlo technique on a tetrahedral lattice. The asphericity A, the ratios <L-2(2)>/<L-1(2)> and <L-3(2)>/<L-1(2)> were calculated for different Values of polymer chain length n, conformational energy epsilon (epsilon greater than or equal to 0) and temperature T. The asphericity A decreases with the increase of chain length and tends to reach its limiting value rapidly with the decrease of gamma (gamma = epsilon/k(B)T). For large n, A is about 0.525 +/- 0.005, the ratios <L-2(2)>/<L-1(2)> and <L-3(2)>/<L-1(2)> are about 2.7 and 12.0, respectively, and are almost independent of gamma, but for short chains, they depend on gamma.

One-dimensional Zigzag Chain Coordination Polymer [Zn(μ-phth)(imi)_2]_∞ Bridged by ο-Phthalato

The reaction of zinc carbonate with o-phthalic acid and imidazole in an aqueous-alcohol solution led to the formation of colorless crystals of [Zn(-phth)(imi)2]∞. Single-crystal X-ray analysis has revealed that the complex crystallizes in a monoclinic system, space group Pn with a = 8.394(2), b = 9.976(3), c = 9.959(3) ? ?= 104.409(4)? V = 807.6(4) ?, Z = 2, C14H12N4O4Zn, Mr = 365.65, Dc = 1.504 g/cm3, ?= 1.544 mm-1, F(000) = 372, the final R = 0.0466 and wR = 0.1171 for 1834 reflections with I >2(I). The complex displays a zigzag infinite chain structure in which each zinc (Ⅱ) center is coordinated by two oxygen atoms and two nitrogen atoms to generate a ZnN2O2 distorted tetrahedral geometry. The neighboring zinc atoms are bridged by the o-phthalate ligand. Each chain is linked by hydrogen bonds with its neighbors to form a three-dimensional coordination polymer.

Synthesis,Crystal Structure and Fluorescence Property of the Ag(Ⅰ) Coordination Polymer Constructed by 2D[Ag(1,3-BIP)(PMA)_(0.5)]_n^(n-)Layers and 1D[Ag(1,3-BIP)(H_2O)]_n^(n+) Chains

A new AgO） coordination polymer, {[Ag（1,3-BIP）（H20）][Ag（1,3- BIP）（PMA）0.5.- 4H20}n （PMA = 1,2,4,5-benzenetricarboxylic acid, 1,3-BIP = 1,3-bis（imidazole）propane）, have been synthesized and characterized by single-crystal X-ray diffraction, powder XRD, FTIR, TGA and elemental analysis techniques. The single-crystal X-ray diffraction reveals that the title complex is formed by 1D polymeric cationic chains of [Ag（1,3-BIP）（H2O）]n^n＋ and 2D polymetric anionic layer of [Ag（1,3-BIP）（PMA）0.5]n^n-, which are further linked by intermolecular H-bonding to form a 3D supramolecular framework. In addition, the photoluminescence property of the title complex in the solid state at room temperature was also investigated.

Stretching strongly confined semiflexible polymer chain

By the so-called wormlike chain （WLC） model in polymer physics envision- ing an isotropic rod that is continuously flexible, the force-extension relations of semi- flexible polymer chains strongly constrained by various confinements are theoretically investigated, including a slab-like confinement where the polymer chains are sandwiched between two parallel impenetrable walls, and a capped nanochannel confinement with a circular or rectangular cross-section where the chains are bounded in three directions. The Brownian dynamics （BD） simulations based on the generalized bead-rod （GBR） model are performed to verify the theoretical predictions.

Rheological Behaviour for Polymer Melts and Concentrated Solutions Part Ⅰ:A New Multiple Reptation Model to Predict the Nonlinear Visco-elasticity with Nagai Chain Constraints in Entangled Polymer Melts

An approach of stochastically statistical mechanics and a unified molecular theory of nonlinear viscoelasticity with constraints of Nagai chain entanglement for polymer melts have been proposed. A multimode model structure for a single polymer chain with n tail segments and N reversible entanglement sites on the test polymer chain is developed. Based on the above model structure and the mechanism of molecular flow by the dynamical reorganization of entanglement sites, the probability distribution function of the end-to-end vectr for a single polymer chain at entangled state and the viscoelastic free energy of deformation for polymer melts are calculated by using the method of the stochastically statistical mechanics. The four types of stress-strain relation and the memory function are derived from this thery. The above theoretical relations are verified by the experimentaf data for various polymer melts. These relations are found to be in good agreement with the experimental results

Syntheses,Structures,and Photoluminescent Properties of Two Zn(Ⅱ)Coordination Polymers with Helical Chains Structures

Two novel coordination polymers with helical chains, {[Zn（L）（H2O）]·H2O}n（1） and {[Zn（L）（p-bix）]·3.5H2O}n（2）, where H2 L = 5-（4-hydroxypyridinium-1-ylmethyl） isophthalic acid and p-bix = 1,4-bis（imidazol-1-ylmethyl）benzene, have been hydrothermally synthesized, and charac-terized by elemental analysis, powder X-ray diffraction（PXRD）, IR, thermal gravimetric analyses（TGA） and also by single-crystal X-ray diffraction. Both complexes 1 and 2 crystallize inmonoclinic, space group P21/c. Compound 1 displays a two-dimensional（2D） structure with two distinct types of helical chains; 2 shows a layered coordination polymer with two types of helical chains and features an interesting 2D→3D interdigitated architecture. Meanwhile, the luminescent properties of 1 and 2 have also been investigated in detail.

RAFT Miniemulsion Polymerization of MMA with Cumyl Dithiobenzoate as Chain Transfer Agent

Reversible addition-fragmentation transfer （RAPT） miniemulsion polymerizations for PMMA with cumyl dithiobenzoate （CDB） as a chain transfer agent （CTA） has been carried out. Higher temperature made the polymerization much faster and the PDI remained below 1.20, when the temperature was upon 70 ℃.

SYNTHESIS OF HETEROARM STAR-SHAPED POLYMER BY THE USE OF POLYFUNCTIONAL CHAIN-TRANSFER AGENT via CONVENTIONAL FREE RADICAL POLYMERIZATION

Heteroarm star-shaped polymers were synthesized by conventional free radical polymerization in two steps by the use of polyfunctional chain transfer agent.In the first step,free radical polymerization of methyl methacrylate was carried out in the presence of a polyfunctional chain transfer agent,pentaerythritol tetrakis(3-mercaptopropinate).At appropriate monomer conversions,two-arm PMMA having two residual thiol groups at the chain center or three-arm PMMA having one residual thiol group at the core were o...

MONTE CARLO STUDY ON THE CRITICAL ADSORPTION POINT OF BONDFLUCTUATED POLYMER CHAINS TETHERED ON ADSORBING SURFACES

The behavior of three-dimensional bond fluctuation model chains tethered on an adsorbing fiat surface was simulated by the Monte Carlo method.The dependence of the number of surface contacts M on the interaction strengthεand the chain length N was investigated by a finite-size scaling law M = N;[a;+a;N;κ+ O((N;κ);)]forεnear the critical adsorption pointε;,i.e.,κ=（ε-ε;）/ε;closes to 0.The critical adsorption point was estimated to beε;=0.93,and the exponentsφ= 0.49 and l/v= 0.57.

STUDY OF CHIRAL SIDE CHAIN LIQUID CRYSTALLINE POLYMERS

Five kinds of side chain liquid crystalline polymers with a chiral component in the pendant group were synthesized and characterized by GPC, polarizing microscopy, DSC, X-ray diffraction ano Dielectric Relaxation Spectroscopy. The liquid crystalline behaviour of the polymers is affected by the length of flexible spacer, which links the mesogenic side chain to the polymer backbone and mesogenic moiety. The characteristic of smectic phase is observed for all the polymers.

DYNAMIC MONTE CARLO STUDY ON THE CORRELATION BETWEEN SHAPE AND SIZE OF LINEAR POLYMER CHAINS

The correlation between shape and size of linear chains on the simple cubic lattice is investigated using a dynamicMonte Carlo technique. A positive correlation between the asphericity parameter A and the square of the end-to-end distanceR^2, as well as that between A and the square of the radius of gyration S^2, is found for both RW and SAW chains, indicatingthat a chain conformation of small size is usually more spherical than one of large size. The result can explain why the shapeof the SAW chain deviate much more from a sphere than that of the RW chain, and can also explain the similar dependenceof size and shape on chain stiffness and on the distance of the first bead of a chain from an infinitely large flat surface.

Dynamic Monte Carlo study on the probability distribution functions of tail-like polymer chain

The configurational properties of tail-like polymer chains with one end attached to a flat surface are studied by using dynamic Monte Carlo technique. We find that the probability distribution of the free end in z direction P（Rz） and the density profile p（z） can be scaled approximately by a factor β to be a length independent function for both random walking （RW） and self-avoiding walking （SAW） tail-like chains, where the factor β is related to the mean square end-to-end distance 〈RE〉. The scaled P（Rz） of the SAW chain roughly overlaps that of the RW chain, but the scaled p（z） of the SAW chain locates at smaller βz than that of the RW chain.

DIGITAL ANALYSIS TECHNOLOGY FOR MORPHOLOGY OF POLYMER CHAIN COILS IN FLOW FIELDS

Polymer chain coils with entanglement is a crucial scale of structures in polymer materials since their relaxationtimes are matching practical processing times.Based on the phenomenological model of polymer chain coils and a new finiteelement approach,we have designed a computer software including solver,pre-and post-processing modules,and developeda digital analysis technology for the morphology of polymer chain coils in flow fields(DAMPC).Using this technology wemay simulate the morphology development of chain coils in various flow fields,such as simple shear flow,elongational flow,and any complex flow at transient or steady state.The applications made up to now show that the software predictions arecomparable with experimental results.

SEGMENT DENSITY PROFILES OF COMPACT POLYMER CHAINS CONFINED BETWEEN TWO PARALLEL PLANE WALLS

We use the pruned-enriched Rosenbluth method to investigate systematically the segment density profiles of compact polymer chains confined between two parallel plane walls. The non-adsorption case of adsorption interaction energy ε = 0 and the weak adsorption case of ε= -1 are considered for the compact polymer chains with different chain lengths N and different separation distances between two walls D. Several special entropy effects on the confined compact polymer chains, such as a damped oscillation in the segment density profile for the large separation distance D, are observed and discussed for different separation distances D in the non-adsorption case. In the weak adsorption case, investigations on the segment density profiles indicate that the competition between the entropy and adsorption effects results in an obvious depletion layer. Moreover, the scaling laws of the damped oscillation period Td and the depletion layer width Ld are obtained for the confined compact chains. Most of these results are obtained for the first time so far as we know, which are expected to understand the properties of the confined compact polymer chains more completely.

A steered molecular dynamics study on the elastic behaviour of knotted polymer chains

In this paper the influence of a knot on the structure of a polymethylene （PM） strand in the tensile process is investigated by using the steered molecular dynamics （SMD） method. The gradual increasing of end-to-end distance, R, results in a tighter knot and a more stretched contour. That the break in a knotted rope almost invariably occurs at a point just outside the ＇entrance＇ to the knot, which has been shown in a good many experiments, is further theoretically verified in this paper through the calculation of some structural and thermodynamic parameters. Moreover, it is found that the analyses on bond length, torsion angle and strain energy can facilitate to the study of the localization and the size of a knot in the tensile process. The symmetries of torsion angles, bond lengths and bond angles in the knot result in the whole symmetry of the knot in microstructure, thereby adapting itself to the strain applied. Additionally, the statistical property of the force-dependent average knot size illuminates in detail the change in size of a knot with force f, and therefore the minimum size of the knot in the restriction of the potentials considered in this work for a PM chain is deduced. At the same time, the difference in response to uniaxial strain, between a knotted PM strand and an unknotted one is also investigated. The force-extension profile is easily obtained from the simulation. As expected, for a given f, the knotted chain has an R significantly smaller than that of an unknotted polymer. However, the scaled difference becomes less pronounced for larger values of N, and the results for longer chains approach those of the unknotted chains.

Reversible addition-fragmentation chain transfer graft polymerization of acrylonitrile onto PE/PET composite fiber initiated by γ-irradiation

Reversible addition-fragmentation chain transfer(RAFT) mediated grafting of acrylonitrile onto Polyethylene/Poly(ethylene terephthalate)(PE/PET) composite fibers was performed using γ-irradiation as the initial source at ambient temperature. Different initial concentrations of 2-cyanoprop-2-yl dithiobenzonate were used as the chain transfer agent. The kinetics of graft polymerization is in accordance with the living RAFT polymerization. The successful grafting of acrylonitrile is proved by Fourier transform infrared spectroscopy analysis.The results of monofilament tensile test show that mechanical properties of the fibers change slightly after grafting. Scanning electronic microscopy images of the fibers show that the surface of RAFT grafted fibers is smoother than that of fibers grafted conventionally.