Ke-Ke Yang

POLY(p-DIOXANONE) AND ITS COPOLYMERS

ABSTRACT This paper reviews the synthesis, properties, and applications of biodegradable polymer, poly(p-dioxanone) (PPDO), and its copolymers. Recent progress in ring-opening polymerization of p-dioxanone employing several effective catalysts is described. Properties of PPDO are given. The copolymers based on PPDO are also discussed.

Properties of Starch Blends with Biodegradable Polymers

Abstract Starch, one of the most inexpensive and most readily available of all natural polymers, can be processed into thermoplastic materials only in the presence of plasticizers and under the action of heat and shear. Poor water resistance and low strength are limiting factors for the use of materials manufactured only from starch, and hence the modification of starch is often achieved by blending aliphatic polyesters. In this review, the literatures concerning the properties of various blends of starch and aliphatic polyesters have been summarized. The biodegradable rates of blends can be controlled to a certain extent depending on the constitutions of blends, and the mechanical properties of blends are close to those of traditional plastics such as polyethylene and polystyrene. The reduction of their sensitivity to humidity makes these materials suitable for the production of biodegradable films, injection-molded items, and foams.

Self-healable and recyclable triple-shape PPDO–PTMEG co-network constructed through thermoreversible Diels–Alder reaction

Based on Diels–Alder reaction, linear bisfuranic terminated poly(tetramethylene oxide) and poly(p-dioxanone) were crosslinked by tris(2-maleimide ethyl)amine; this process was fully reversible under moderate conditions. All of the results indicate that the co-network possesses the typical advantages of chemical and physical crosslinking, peculiar thermal invertibility, shape memory effect and self-healability.

Structure and Properties of Soy Protein/Poly(butylene succinate) Blends with Improved Compatibility

A novel environmentally friendly thermoplastic soy protein/polyester blend was successfully prepared by blending soy protein isolate (SPI) with poly(butylene succinate) (PBS). To improve the compatibility between SPI and PBS, the polyester was pretreated by introducing different amounts of urethane and isocyanate groups before blending. The blends containing pretreated PBS showed much finer phase structures because of good dispersion of polyester in protein. Consequently, the tensile strength and modulus of blends increased obviously. A lower glass transition temperature of protein in the blends than that of the pure SPI, which was caused by the improvement of the compatibility between two phases, was observed by dynamic mechanical analyzer (DMA). The hydrophobicity, water resistance, and moisture absorption at different humidities of the blends were modified significantly due to the incorporation of PBS.

Kinetics of thermal degradation and thermal oxidative degradation of poly(p-dioxanone)

Abstract The kinetics of the thermal degradation and thermal oxidative degradation of poly(p-dioxanone) (PPDO) were investigated by thermogravimetric analysis. Kissinger method, Friedman method, Flynn–Wall–Ozawa method and Coats–Redfern method have been used to determine the activation energies of PPDO degradation. The results showed that the thermal stability of PPDO in pure nitrogen is higher than that in air atmosphere. The analyses of the solid-state processes mechanism of PPDO by Coats–Redfern method and Criado et al. method showed: the thermal degradation process of PPDO goes to a mechanism involving random nucleation with one nucleus on the individual particle (F1 mechanism); otherwise, the thermal oxidative degradation process of PPDO is corresponding to a nucleation and growth mechanism (A2 mechanism).

Kinetics of thermal oxidative degradation of phosphorus-containing flame retardant copolyesters

Abstract The thermal oxidative degradation of phosphorus-containing copolyester and poly(ethylene terephthalate) (PET) in air were studied by thermogravimetric analysis (TG) in order to obtain the activation energies of pyrolysis. The activation energies were determined using the Kissinger method and the Flynn–Wall–Ozawa method, which do not require knowledge of the reaction mechanism (RM). The results show that there is no large difference between the values of activation energy of phosphorus-containing copolyester and PET, which suggests that the flame retardants studied do not greatly influence the mechanisms of pyrolysis.

Novel poly(tetramethylene ether)glycol and poly(ε-caprolactone) based dynamic network via quadruple hydrogen bonding with triple-shape effect and self-healing capacity.

A novel dynamic network was successfully prepared via self-complementary quadruple hydrogen bonding through Upy-telechelic poly(tetremethylene ether) glycol (PTMEG) and four-arm star-shaped poly(ε-caprolactone) ((4)PCL) precursors. The structure and the dynamic feature were identified by FT-IR and (1)H NMR. The differential scanning calorimetry (DSC) analysis indicated that the crystalline PCL and PTMEG segments show a separated melting peak, and the aggregation of Upy dimer was also observed. The dynamic mechanical analyzer (DMA) test reveals that the storage modulus of the network drops evidently across the thermal transition. These characteristics of the network ensure that it exhibits a triple-shape effect, and the composition of the network influences the performance of shape memory effect. The variation of the fixing ratio of the network in each deformation step is quite according to the crystallinity of the dominant segment. The reversibility of the quadruple hydrogen bonding between Upy dimer endues the network with self-healing capacity, and the damage and healing test of the network revealed that increasing the content of the PTMEG segment will be of benefit to self-healing performance.

Poly(butylene succinate)-poly(ethylene glycol) multiblock copolymer: Synthesis, structure, properties and shape memory performance

Thermally-induced shape memory multiblock poly(ether-ester)s (PBSEGs) comprising crystallisable poly(butylene succinate) (PBS) hard segments and poly(ethylene glycol) (PEG) soft segments, were synthesized by polycondensation from succinic acid, 1,4-butanediol and PEG diol. The copolymers were characterized by 1H-NMR, GPC, DSC and DMA. DSC analysis revealed that all PBSEGs prepared in this work are double-crystalline copolymers which ensure it to form separated crystalline domain determined the permanent shape and temporary shape respectively. The Tm of PEG segment (Tm,PEG) of the PBSEGs ranging from 27.54 to 51.04 °C, acting as the transition temperature (Ttrans), was controllable by varying the chain length of soft segment. The DMA test indicated that a large difference in modulus below and above the Ttrans of PBSEGs endows it with sufficient deformability at high temperature and high capacity for keeping deformation at low temperature. The mechanical properties of the copolymer films were assessed by tensile strength measurement. It showed that the copolymers were ductile which enabled remarkable reversible deformation. The shape memory properties of PBSEGs were evaluated by bending test, as expected, most copolymers possessed excellent shape memory effect. The contact angle tests demonstrated that the copolymers were more hydrophilic with the introduction of PEG segment, suggesting this biodegradable PBSEG multiblock copolymer with excellent shape-memory properties has great potential in application for biomaterials.

Design of Poly(l-lactide)–Poly(ethylene glycol) Copolymer with Light-Induced Shape-Memory Effect Triggered by Pendant Anthracene Groups

A novel light-induced shape-memory material based on poly(l-lactide)-poly(ethylene glycol) copolymer is developed successfully by dangling the photoresponsive anthracene group on the PEG soft segment selectively. For synthesis strategy, the preprepared photoresponsive monomer N,N-bis(2-hydroxyethyl)-9-anthracene-methanamine (BHEAA) is first embedded into PEG chains; then, we couple this anthracene-functionalized PEG precursor with PLA precursor to result in PLA-PEG-A copolymer. The composition of target product can be well-defined by simply adjusting the feed ratio. The chemical structures of intermediate and final products are confirmed by (1)H NMR. Differential scanning calorimetry analysis of material reveals that the PEG soft segment became noncrystallizable when 4% or more BHEAA is introduced, and this feature is beneficial to the mobility of anthracene groups in polymer matrix. The static tensile tests show that the samples exhibit rubberlike mechanical properties except for the PLA-dominant one. The reversibility of [4 + 4] cycloaddition reaction between pendant anthracene groups in PLA-PEG-A film is demonstrated by UV-vis. Eventually, the light-induced shape-memory effect (LSME) is successfully realized in PLA-PEG-A. The results of cyclic photomechanical tests also reveal that the content of PLA hard segment as well as photosensitive anthracene moieties plays a crucial role in LSME.

Thermogravimetric analysis of the decomposition of poly(1,4-dioxan-2-one)/starch blends

Abstract Thermal degradation of poly (1,4-dioxan-2-one)/starch was studied by thermogravimetric analysis in order to determine the actual reaction mechanism (RM) of the decomposition. The activation energy of the solid state process was determined using Kissingers method, which does not require knowledge of the RM, whose result is 121 kJ/mol. Different integral and differential methods were used to compare with this value. Also, the experimental results were compared to master curve plots in the range of Doyle approximations. Analysis of experimental results suggests that in the range of conversions studied, 5–20%, the actual RM is D 3 type, which is three-dimensional diffusion. The addition of starch will not change the recyclability of PPDO.