5Carbon dioxide based oligo(carbonate-ether) diol (CO 2 -polyol) with both carbonate units and ether units in one polymer chain were prepared from copolymerization of CO 2 and propylene oxide (PO) using zinccobalt double metal complex as catalyst, and used to prepare CO 2 based waterborne polyurethane (CO 2 -WPU). The carbonate units in CO 2 -polyol improved the mechanical and oxidation resistance properties of CO 2 -WPU, while the ether units in CO 2 -polyol enhanced the hydrolysis resistance of CO 2 -WPU. The 10 tensile strength of CO 2 -WPU didn't show obvious drop during immersion in 0.25% sodium hydroxide solution, whereas that of oligoesterol based WPU dropped over 50% after 300 min, and lost mechanical property after 520 min immersion. Meanwhile, the retention of tensile strength of CO 2 -WPU was Ca.72% even after 46 h immersion in 6 wt% H 2 O 2 solution, while that was only Ca.32% for oligoetherol based WPU. Moreover, the thermal-mechanical performance of CO 2 -WPU film can be conveniently adjusted by 15 carbonate unit content (CU%) in CO 2 -polyol, i.e., when CU% in CO 2 -polyol increased from 30% to 66%, the glass transition temperature (T g ) increased from -7.8 0 C to 18.8 0 C, accompanied by an increase of tensile strength from 35.6 MPa to 52.2 MPa, a decrease of elongation at break from 630% to 410%. This work suggests that the CO 2 -WPU may be promising alternative for conventional WPU whose oligoetherol and oligoesterol were from fossil resources, and its comprehensive hydrolysis/oxidation 20 resistance may be a bonus unavailable from common oligomerol based WPU. 65 75%. 13 Recently, there is a nice report from Bardow that CO 2polyol may be viable alternative in polyurethane industry from an environmental point of view based on life cycle assessment. 14 We are wondering whether polyol derived from CO 2 and PO is suitable oligomerol for WPU. Up to now, however, there is few 70 reports on such issue.

Controllable synthesis of a narrow polydispersity oligo(carbonate-ether) tetraol provided a new relationship between the acidity (pKa1 value) of the chain transfer agent and the catalytic mechanism in the initial stage.

No abstract

A novel aliphatic polycarbonate from renewable resource was prepared by copolymerization of furfuryl glycidyl ether and CO2 using rare earth ternary catalyst; its number-average molecular weight (M n) reached 13.3 × 104 g/mol. The furfuryl glycidyl ether and CO2 copolymer (PFGEC) was easy to become yellowish at ambient atmosphere due to postpolymerization cross-linking reaction on the furan ring; the gel content was 17.2 wt % after 24 h exposure to air at room temperature. PFGEC could be stabilized by addition of antioxidant 1010 (tetrakis[methylene (3,5-di(tert-butyl)-4-hydroxyhydrocinnamate)]methane) in 0.5−3 wt % after copolymerization. The Diels−Alder (DA) reaction between N-phenylmaleimide and the pendant furan ring was also effective for the stabilization of PFGEC by reducing the amount of furan ring and introducing bulky groups into PFGEC. The cyclization degree could reach 72.1% when the molar ratio of N-phenylmaleimide to furan ring was 3:1, and no gel was observed after 24 h exposure to air. The glass transition temperature (T g) of PFGEC was 6.8 °C, and it increased to 40.3 °C after DA reaction (molar ratio of N-phenylmaleimide to furan ring was 3:1). A third way was also conducted to solve the air instability of PFGEC, where tetrahydrofurfuryl glycidyl ether, a hydrogenated furfuryl glycidyl ether, was used instead of furfuryl glycidyl ether for air-stable polycarbonate, and a copolymer with M n of 7.7 × 104 g/mol and T g of −5.7 °C was synthesized.

Due to the concern on residue toxic metal in biodegradable poly(propylene carbonate) (PPC), soil tolerant and heavy metal free aluminum complexes, that is, bifunctional aluminum porphyrin catalysts bearing quaternary ammonium salts on the ligand framework were prepared. Variation of the quaternary ammonium anion and the axial ligand had dramatic effects on the catalytic activity of resultant complex, among which complex 3b yielded perfectly alternative PPC with high molecular weight and relatively narrow polydispersity, and its TOF reached 3,407 h 21 at [PO]/[cat.] ratio of 20,000 at 110 C, although the PPC selectivity was 71%. By introducing specific substituent on the ligand framework, the electronic environment at the active center can be changed, among which complex 5b bearing tertiary butyl-functionalized aryl substituents exhibited a TOF of 449 h 21 at [PO]/[cat.] ratio of 5,000 at 70 C, with PPC selectivity of 92% and number average molecular weight of 36 kg mol 21 .

Whole-procedure solvent-free preparation of CO2-WPU was accomplished by direct dispersion of the prepolymer at an elevated temperature.

No abstract

A novel design of a two-mode de/multiplexer (DE/MUX) based on multimode interference (MMI) couplers is presented. Instead of the phase shifter (PS) in the shape of a narrow strip waveguide, which needs tight design and fabrication requirements, a tilted joint is used as a PS in the proposed device, so that the effects of the fabrication errors of the PS on the performance of the device can be reduced greatly. Simulations show that while the size of the device is as small as 39.54 μm, which is more compact than other MMI-based DE/MUX, the fabrication tolerance is larger than ±25  nm. Within the entire C-band wavelength range, the de-multiplexing crosstalk of the device is lower than -28  dB and the insertion loss is below 1.0 dB.