Potassium Acetate/18-Crown-6 Pair:Robust and Versatile Catalyst for Synthesis of Polyols from Ring-Opening Copolymerization of Epoxides and Cyclic Anhydrides

Efficient synthesis of polyester polyols with tunable molecular weight and microstructures from cyclic anhydride/epoxide mixtures by taking advantage of chain transfer reaction remains a great challenge,because most of the catalysts exhibit poor tolerance to chain transfer agent(CTA).In this contribution,we demonstrated that potassium acetate(KOAc)and 18-crown-6(18-C-6)combination has great potential in the synthesis of diverse polyester polyols with controllable molecular weight and high-end group fidelity.Com-pared with KOAc,KOAc/18-C-6 pair could induce a much faster chain transfer between the active and dormant chains,and thus produce polyester polyols with narrow and monomodal distribution.In addition,polyester polyols could be efficiently prepared in laboratory by using commercially available cyclic anhydride without further purification(containing about 2%diacid residual as CTA)with an extremely low catalyst loading([catalyst pair]:[anhydride]:[epoxide]=1:50000:250000,[catalyst pair]=0.0004 mol%).KOAc/18-C-6 could also promote the self-switchable copolymerization of cyclic anhydride/epoxide/cyclic ester mixtures.Ring-opening copolymerization of cyclic ester was initiated automatically after the full conversion of cyclic anhydride,finally producing polyester polyols with ABA-type block structure.

Monomer-activated Copolymerization of Ethylene Oxide and Epichlorohydrin: In Situ Kinetics Evidences Tapered Block Copolymer Formation

The monomer-activated anionic ring-opening copolymerization (AROP) of ethylene oxide (EO) and epichlorohydrin (ECH) using tetraoctylammonium bromide as an initiator and triisobutylaluminum (i-Bu3Al) as an activator was studied. The properties of the copolymers as well as the microstructure have been analyzed in detail via an in situ NMR kinetics study. The statistical copolymers exhibited molecular weights ranging from 2350 g·mol^-1 to 38000 g·mol^-1 (measured by SEC, PEG-standards) and moderate dispersities of 1.27-1.44. The thermal property tests revealed both a glass transition and melting for all copolymers, supporting a block-like nature. Applying in situ NMR kinetic measurements, the reactivity ratios of EO and ECH were determined to be strongly disparate, i.e., rEo = 9.2 and rECH = 0.10. This shows that the simple one-pot statistical anionic copolymerization of EO and ECH via the monomer-activated AROP resulted in the formation of strongly tapered, block-like structures. Furthermore, post-polymerization functionalization of the reactive chloromethyl groups by nucleophilic displacement was investigated for the copolymers. Copolymerization of EO and ECH offers a broad platform for further functionalization and therefore the possibility to prepare a variety of multifunctional PEGs.

2D Naphthalenedisulfonate-cadmiun coordination polymer with2,4,5-tri(4-pyridyl)-imidazole as a co-ligand:Structure and catalytic property

A new 2D coordination polymer, [Cd（tpim）（1,5-nds）]n （1）, was constructed from 1,5-naphthalenedi- sulfonate （1,5-nds）. 2.4,5-tri（4-pyridyl）-imidazole （tpim） and Cd（CH3COO）2.2H2O, which can be subsequently used to promote the epoxide ring-opening reaction of epoxides and amines with remarkable catalytic activity. In addition, the thermal and luminescent properties of I in the solid state were also investigated.

Synthesis and characterization of castor oil-based polymeric surfactants

Dehydrated castor oil was epoxidized using phosphoric acid as a catalyst and acetic acid peroxide as an oxidant to produce epoxidized castor oil(ECO). Ringopening polymerization with stannic chloride was used to produce polymerized ECO(PECO), and sodium hydroxide used to give hydrolyzed PECO(HPECO). The HPECO was characterized by Fourier transform infrared,1H and13 Cnuclear magnetic resonance spectroscopies,gel permeation chromatography, and differential scanning calorimetry. The weight-average molecular weight of soluble PECO and HPECO were 5026 and2274 g$mol^(–1), respectively. PECO and HPECO exhibited glass transition. Through neutralizing the carboxylic acid of HPECO with different counterions, castor oil-based polymeric surfactants(HPECO-M, where M = Na^+, K^+or triethanolamine ion) exhibited high ef ficiency to reduce the surface tension of water. The critical micelle concentration(CMC) values of HPECO-M ranged from0.042 to 0.098 g$L^(–1)and the minimum equilibrium surface tensions at CMC(g cmc) of HPECO-M ranged from 25.6 to30.0 m N$m^(–1). The water-hexadecane interfacial energy was calculated from measured surface tension using harmonic and geometric mean methods. Measured values of water-hexadecane interfacial tension agreed well with those calculated using the harmonic and geometric mean methods.