Ying Guan

Hydrogen-bonded polymer network-poly(ethylene glycol) complexes with shape memory effect

Complexes of a poly(methacrylic acid-co-methyl methacrylate) network with poly(ethylene glycol) stabilized by hydrogen bonds were prepared. By introducing poly(ethylene glycol), the complexes possessed shape memory effect, due to which a large difference in storage modulus below and above the glass transition temperature occurred. The morphology of the complexes was investigated and the mechanism of the shape memory behavior was discussed. This kind of complexes can be regarded as a novel shape memory network.

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 n[=u200616.7, 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.

Complex of polyelectrolyte network with surfactant as novel shape memory networks.

Poly(acrylic acid-co-methyl methacrylate)-cetyltrimethylammonium bromide (P(AA-co-MMA)-C16TAB) complex has shape memory behavior due to the formation of crystalline aggregates among the long alkyl chains of C16TAB in the complex, and can be regarded as a novel shape memory network.

Investigation of the gelation process by in‐situ interferometry

An in-situ interferometric technique was established to investigate the gelation process of poly(acrylic acid) (PAA) gel. The basic principles of the in-situ interferometric technique is illustrated. It can provide sufficient information for a non-destructive and successful investigation throughout the whole gelation process. Moreover, the effect of the photoinitiator concentration on the gelation process was studied. The polymerization rate of AA increases with increasing the concentration of the photoinitiator. The error caused by thermal effects during the gelation process can be neglected.

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.