Shaojun Chen

A review of actively moving polymers in textile applications

Actively moving polymers being developed rapidly have drawn wide attention. A review is presented to highlight the most important areas and directions in textile applications. The molecular structure of actively moving polymers is introduced firstly. The textile applications of actively moving polymers are then summarized from the fibre spinning (including wet spinning, melt spinning and electro-spinning), fabric manufacturing, shape memory finishing technologies and water vapor permeability investigation. Additionally, the challenges of actively moving polymers in textile applications are pointed out and some research directions are suggested.

Facile preparation and synergistic antibacterial effect of three-component Cu/TiO2/CS nanoparticles

Due to the outbreaks of infectious diseases caused by different pathogenic bacteria and development of antibiotic resistance, researchers are actively searching for new antibacterial agents. Synergistic antibacterial effects provide a new way to prepare antibacterial systems to fight resistant bacteria. In this study, novel copper (Cu)/titanium dioxide (TiO2)/chitosan (CS) (CTC) three-component nanoparticles were facilely prepared via photocatalytic reduction on the basis of the synergistic antibacterial principle. The structure, antibacterial activity and antibacterial mechanism of CTC were investigated systematically. The results showed that this hybrid material exhibits excellent antibacterial ability against Escherichia coli and Staphylococcus aureus due to the synergistic antibacterial effect of the Cu, TiO2 and CS components in the nanoparticles. The minimal inhibition concentrations (MIC) of CTC against E. coli and S. aureus are only 5.22 μg mL−1 and 2.61 μg mL−1, respectively, much lower than the two-component systems. Thus, the encouraging results presented in this study demonstrate great potential applications of CTC as an alternative candidate for an antibacterial agent with high antibacterial activity.

Enhanced water-solubility and antibacterial activity of novel chitosan derivatives modified with quaternary phosphonium salt

Chitosan (CS) has been widely recognized as an important biomaterial due to its good antimicrobial activity, biocompatibility and biodegradability. However, CS is insoluble in water in neutral and alkaline aqueous solution due to the linear aggregation of chain molecules and the formation of crystallinity. This is one of the key factors that limit its practical applications. Therefore, improving the solubility of CS in neutral and alkaline aqueous solution is a primary research direction for biomedical applications. In this paper, a reactive antibacterial compound (4-(2,5-Dioxo-pyrrolidin-1-yloxycarbonyl)-benzyl)-triphenyl-phosphonium bromide (NHS-QPS) was synthesized for chemical modification of CS, and a series of novel polymeric antimicrobial agents, N-quaternary phosphonium chitosan derivatives (N-QPCSxy, x=1-2,y=1-4) were obtained. The water solubilities and antibacterial activities of N-QPCSxy against Escherichia coli and Staphylococcus aureus were evaluated compare to CS. The water solubility of N-QPCSxy was all better than that of CS at neutral pH aqueous solution, particularly, N-QPCS14 can be soluble in water over the pH range of 3 to 12. The antibacterial activities of CS derivatives were improved by introducing quaternary phosphonium salt, and antibacterial activity of N-QPCSxy increases with degree of substitution. Overall, N-QPCS14 represents a novel antibacterial polymer material with good antibacterial activity, waters solubility and low cytotoxicity.

Development of zwitterionic polyurethanes with multi-shape memory effects and self-healing properties

Recently, multi-shape-memory polymers have attracted significant attention due to their technological impact. This study reports novel zwitterionic multi-shape-memory polyurethanes (ZSMPUs) from N-methyldiethanolamine (MDEA), hexamethylene diisocyanate (HDI) and 1,3-propanesultone (PS). The ZSMPUs feature excellent multi-shape-memory properties that are capable of remembering four different shapes, and shape recovery decreases with increasing sulfobetaine content. Ionic interactions greatly influence the structure, morphology and properties. Increasing the sulfobetaine content promotes the phase mixing and zwitterions serve as organic fillers in the zwitterionic polyurethane. Immersing the zwitterionic polyurethane in moisture-rich conditions and drying at low temperature preserves the shape-memory capabilities and demonstrates good self-healing properties. Furthermore, both the shape memory effect and self-healing effects are repeatable. The self-healing mechanism is ascribed to the spontaneous attraction of zwitterions, followed by slower re-entanglement.

Effect of steaming on shape memory polyurethane fibers with various hard segment contents

To illustrate the effect of post-treatment high-pressure steaming and hard segment content on shape memory polyurethane (SMPU) fiber, a series of shape memory polyurethane having various hard segment contents was synthesized with the pre-polymerization method, spun with a wet spinning process and treated with high pressure saturated water vapor. Differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), wide angle x-ray diffraction (WAXD), mechanical testing and cyclic tensile testing were conducted to investigate the particular thermal/mechanical properties, crystallization of hard segments and shape memory properties of SMPU fibers. In addition, in the light of a comparison between the original and the treated SMPU fiber, the effect of steaming post-treatment in SMPU fibers with various hard segment contents was illustrated. The steaming treatment gives rise to a higher elongation ratio at break, lower tenacity and initial modulus. Hard segment crystallization can be induced, especially in fiber with higher hard segment content after treatment. The glass transition temperature of the soft segment of SMPU fibers was decreased after steaming and the trends are most likely significant in high hard segment content specimens. Steaming with high pressure saturated water vapor can eliminate the thermal shrinkage and provide dimensional stability to the original SMPU fibers. The recoverability remains well in all treated specimens, but the fixity ability decreases with the decrease of hard segment content.

Insights into liquid-crystalline shape-memory polyurethane composites based on an amorphous reversible phase and hexadecyloxybenzoic acid

Liquid-crystalline polymers and shape-memory polymers are attractive to many researchers. This paper proposes a strategy to prepare liquid-crystalline shape-memory polyurethane (LC-SMPU) composites having both liquid-crystalline properties and shape-memory properties. A series of LC-SMPU composites are successfully prepared by doping different concentrations of 4-hexadecyloxybenzoic acid (HOBA) into shape-memory polyurethanes (SMPUs). The results show that the HOBA is physically mixed with the polyurethane matrix. The doped HOBA is categorised as HOBA captured by the polyurethane chains and free HOBA in the LC-SMPU composite. A higher content of HOBA results in a higher fraction of free HOBA, and more HOBA molecules enter into the polyurethane matrix at higher annealing temperatures. The resulting LC-SMPU composites keep their intrinsic liquid-crystalline properties and the crystallisation properties of HOBA. The LC-SMPU composites contain a two-phase, separated structure: a HOBA crystalline phase and the polyurethane matrix. Thus, the LC-SMPU composites show a two-stage decrease in modulus. Finally, shape-memory tests show that the LC-SMPU composites exhibit a triple shape-memory effect; in the first step, strain recovery is associated with the glass transition of the amorphous polyurethane matrix, and in the second step, strain recovery results from the melting transition of the HOBA crystal dopants.

Development of supramolecular liquid-crystalline polyurethane complexes exhibiting triple-shape functionality using a one-step programming process

Supramolecular liquid crystalline polymers and shape memory polymers are attracting increasing interest as materials. In this paper, we describe the development of a supramolecular liquid crystalline shape memory polyurethane (SLCSMPU) complex that exhibits both liquid crystalline properties and shape memory properties. The complex is formed by incorporating 4-hexadecyloxybenzoic acid (HOBA) into a pyridine-containing shape memory polyurethane (PySMPU). The HOBA is tethered to the PySMPU by strong hydrogen bonding between the pyridine rings and the COOH of the HOBA, forming a SLCSMPU complex. Heat treatment plays an important role in the formation of hydrogen-bonded supramolecular liquid crystalline structures in these SLCSMPU complexes. Thus, the SLCSMPU complex not only maintains the intrinsic liquid-crystalline properties of HOBA, but can also form a stable polymeric film for various shape memory applications. Additionally, the SLCSMPU complex forms a two-phase separated structure composed of an amorphous polyurethane matrix and a HOBA crystalline phase, which includes the hydrogen-bonded crystalline HOBA phase and the free HOBA crystalline phase. Therefore, a simple one-step programming process is developed that produces SLCSMPU complexes with excited triple-shape functionalities due to their multiple phase transitions, especially when the molar ratio of HOBA/BINA is less than 0.8.

Development of zwitterionic copolymers with multi-shape memory effects and moisture-sensitive shape memory effects

Shape memory polymers (SMP) and zwitterionic polymers both have great applications in biomedical fields. This works successfully combines functionalities of zwitterionic polymers and SMP, developing new kind of zwitterionic copolymers having a multi-shape memory effect (SME) and a moisture-sensitive SME. The results demonstrate that a series of zwitterionic multi-SMPs, coded as p(DMAPS-co-AA), were synthesized from DMAPS and acrylic acid (AA). A micro-phase separated structure is formed in the resulting p(DMAPS-co-AA). The strong hydrogen bonding between AA segments serves as a reversible switch, while the strong electrostatic forces among DMAPS segments serve as physical crosslinkers. Therefore, shape memory testing demonstrates that p(DMAPS-co-AA) shows not only dual-SME, but also triple-SME and quadruple-sSME. Moreover, in addition to the thermally-induced SME, p(DMAPS-co-AA) also shows moisture-sensitive SME. It is thus proposed that this zwitterionic multi-SMP could find great potential applications in smart biomedical fields.

Study on the structure and morphology of supramolecular shape memory polyurethane containing pyridine moieties

Fabricating smart materials has been an attractive research topic in recent years. In this study, a series of pyridine-containing shape memory polyurethanes (Py-SMPUs) with different pyridine contents were synthesized. Based on the theoretical analysis, the structure and morphology of Py-SMPUs were studied systematically with FT-IR, DSC, WAXD, DMA, AFM, etc. Results show that a hydrogen-bonded supramolecular structure is formed in the Py-SMPUs. Hydrogen bonds present in the urethane group and pyridine ring are the most favorable hydrogen bonds which play an important role in the movement of the polymer chain. Microphase separation consisting of a soft phase and hard phase occurs in the Py-SMPUs. The soft phase is influenced greatly by the N, N-bis(2-hydroxyl ethyl) isonicotinamide (BINA) unit and the hard phase is mainly a result of the hexamethylene diisocyanate and 1,4-butanediol (HDI–BDO) units. As the BINA content decreases, the soft phase tends to change gradually from a continuous amorphous phase to a droplet-like dispersion phase, whereas the hard phase develops from a droplet-like dispersion amorphous phase to a continuous crystalline phase.

Development of liquid-crystalline shape-memory polyurethane composites based on polyurethane with semi-crystalline reversible phase and hexadecyloxybenzoic acid for self-healing applications

Shape memory materials and self-healing materials have attracted considerable attention in recent years. This paper reports the development of a liquid-crystalline shape-memory-polyurethane (LC-SMPU) composite based on SMPU and hexadecyloxybenzoic acid (HOBA) for self-healing applications. The results demonstrate that HOBA is physically mixed with SMPU resulting in a semi-crystalline reversible phase and forming LC-SMPU composites. The two-phase separated structure comprises an SMPU matrix and a HOBA phase. The HOBA phase exhibits a reversible nematic phase within a temperature range of 101–130 °C, while the SMPU matrix acts as a stable polymeric film for various applications. Both the semi-crystalline soft phase of the SMPU matrix and the HOBA crystalline phase can be used to trigger shape memory effects. The LC-SMPU composites display not only triple-shape memory behaviours but also self-healing behaviours due to the heating-induced “bleeding” behaviour of HOBA in the liquid crystalline state and their subsequent recrystallisation upon cooling.