Wenchuan Zhang

Carbon nanotube–polyaniline hybrid materials

Abstract A hybrid material of carbon nanotubes (CNTs)–polyaniline (PANI) was prepared by in situ emulsion polymerization. The structural characterization showed that some CNTs were linked up by PANI chains, which appears to be like a network including PANI fiber and nanotubes. This network results in the hybrid material having highly conductivity with new conductive passageway. The conductivity and thermal properties of hybrid materials depend on the content of CNTs. The CNTs do not affect the structure of PANI chains.

Adsorption/desorption of protein on magnetic particles covered by thermosensitive polymers

The adsorption and desorption behavior of protein human serum albumin (HSA) on magnetic polymer particles covered by thermosensitive polymers was investigated. The results showed that adsorption was dependent mainly on the properties of the particle surface. By increasing the temperature, particles deswelled and were susceptible to absorb larger amounts of proteins, which could be desorbed at lower temperature. The extent of adsorption was found to depend on the pH value, protein concentration, and incubation time. At higher pH, a smaller amount of proteins could be absorbed because of the electrostatic repulsive force between the protein and the surface particles. Increasing incubation time or initial protein concentration was favorable to the adsorption of proteins.

Polytetrahydrofuran Amphiphilic Networks, 5. Synthesis and Swelling Behavior of Thermosensitive Poly(N-isopropylacrylamide)-l-polytetrahydrofuran Networks

A series of thermosensitive and thermoreversible poly(N-isopropylacrylamide)-l-polytetrahydrofuran (PNIPAAm-l-PTHF) amphiphilic networks were synthesized by free-radical copolymerization of N-isopropylacrylamide with the macromolecular crosslinker polytetrahydrofuran diacrylate (PTHFDA). The resulting PNIPAAm-l-PTHF networks show not only the properties of PNIAPPm and PTHF segments, but also the combined properties of the two segments. These networks are amphiphilic and their swelling is composition-dependent both in water and in organic solvents. The relationship of their equilibrium swelling ration (SR e ) and the content of network (W PTHF ) in organic solvents can be defined as: SR e = A* W PTHF + B. They present four solubility parameters that correspond to the hydrophobic and hydrophilic segments of networks. The swelling dynamics of the networks in water in a non-Fickian process, while in cyclohexane they approaches a Fickian process when the PTHF content is about 50-60%. Due to the presence of PTHF segments, the temperature effect on the swelling behavior of the PNIPAAm-l-PTHF networks is significantly different from other reported PNIPAAm copolymers or networks .The thermosensitivity and thermoreversibility of these networks is composition-dependent.

Preparation and characterization of magnetic amphiphilic polymer microspheres

Magnetic amphiphilic polymer microspheres were prepared by copolymerization of styrene with poly(ethylene oxide) macromonomer (MPEO) in the presence of Fe3O4 magnetic fluid in ethanol/water medium. Magnetic microsphere size, size distribution, and surface morphology were characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The structure of copolymer was determined by infrared spectroscopy. With increasing MPEO used in the polymerization, the resulting microsphere size decreased. Magnetic amphiphilic polymer microspheres containing 0.02–0.2 mmol/g hydroxyl groups could be prepared by using different MPEO concentration.

Polytetrahydrofuran amphiphilic networks. I. Synthesis and characterization of polytetrahydrofuran acrylate ditelechelic and polyacrylamide‐l‐polytetrahydrofuran networks

A series of novel amphiphilic polyacrylamide-l-polytetrahydrofuran (PAm-l-PTHF) networks were prepared by the free-radical copolymerization of hydrophobic ditelechelic polytetrahydrofuran acrylate (PTHFDA) with hydrophilic acrylamide. PTHFDA was synthesized by acrylation of the corresponding hydroxycapped PTHF with acrylic acid in cyclohexane. After acrylation, there was no significant difference in the molecular weights and molecular weight distributions between the original PTHF and the resulting PTHFDA. Network structures and compositions were characterized by elemental analyses, Fourier transform infrared, differential scanning calorimetry, scanning electron microscopy, and swelling data. The networks can swell both in organic solvents and in water, which indicates that they are amphiphilic. The swelling of the networks in different solvents is composition-dependent. According to differential scanning calorimetry, scanning electron microscopy, and swelling tests, the networks have a microphase-separated and bicontinuous morphology.

Polytetrahydrofuran amphiphilic networks

The swelling behavior of polyacrylamide-l-polytetrahydrofuran (PAm-l-PTHF) amphiphilic networks was studied in detail. Four solubility parameters δ [= 16.7, 23.3, 30.2 and 47.3 (MPa)1/2] were obtained. The values of 16.7 and 47.3 (MPa)1/2 correspond to the interaction of the PTHF and PAm segments with solvent, respectively, while the other two reflect the synergistic effect of the two phases during swelling. In acetone–water mixture no “volume phase transition” occurs, but the same synergistic effect renders a maximum swelling at certain mixture compositions. In aqueous solution the networks are sensitive to ionic strength when the ionic strength is low. A dynamic study reveals that the swelling of the networks in both water and cyclohexane is a non-Fickian diffusion process. The swelling behavior is entirely due to the microphase-separated and bicontinuous structure of the amphiphilic networks.

Preparation of polytetrahydrofuran monomethacrylate macromonomers by cationic ring‐opening polymerization of tetrahydrofuran

Polytetrahydrofuran monomethacrylate (MA-PTHF) macromonomer was prepared by cationic ring-opening polymerization(CROP) of tetrahydrofuran (THF) using boron trifloride etherate (BF3 · OEt2) as initiator and epichlorohydrin (ECH) as promoter. Two kinds of transfer agents were used: methacrylic acid (represented as TA1), and a mixture of methacrylic acid and sodium methacrylate (represented as TA2). The effects of polymerization conditions on molecular weight and molecular weight distribution of macromonomers were studied in this article, when the composition of reactants was kept constant. Under the same conditions, the molecular weight of macromonomer using TA2 is lower than that using TA1, which indicates that TA2 is more active than TA1. The molecular weight of MA-PTHF macromonomer varies with the polymerization time before transfer agents were added (T1), but molecular weight distribution remains constant. When T1 is limited in 30 min, the apparent number-average molecular weight of MA-PTHF increases significantly with the increase of T1, and ranges from 5000 to 18,000. Hence, the molecular weight of MA-PTHF macromonomer can be controlled by varying T1.

POLYELECTROLYTE NETWORK-SURFACTANT COMPLEXES WITH SHAPE MEMORY EFFECT

The complex of Poly(acrylic acid-co-acrylamide) network with cetyltrimethylammonium bromide (P(AA-co-Am)-C16 TAB) was synthesized. It has shape memory behavior due to the formation of thermodynamically homogeneous structure. A specific feature of this type of shape memory complex is that the transition temperature at which the complex abruptly becomes soft and deforms can be controlled by changing the degree of cross-linkage, which enables one to adjust the shape memory effect at desired temperature. Mechanism and process of the shape memory behavior were discussed.