Selective Ring-Opening Polymerization of Non-Strained γ-Butyrolactone Catalyzed by A Cyclic Trimeric Phosphazene Base

N-Heterocyclic olefins and thioureas as an efficient cooperative catalyst system for ring-opening polymerization of δ-valerolactone

An organocatalytic ring-opening polymerization of δ-valerolactone has been developed.

Preparation of a mimetic and degradable poly(ethylene glycol) by a non-eutectic mixture of organocatalysts (NEMO) via a one-pot two-step process

A one-pot, two-step method for the preparation of degradable PEG is here presented. The full process addresses the requirements imposed by green chemistry and involves the use of a single and nontoxic non-eutectic mixture of organocatalysts. The strategy relies on the polycondensation of PEG800 after its functionalization by bio-derived 5-membered γ-butyrolactone.

A one-pot, two-step method for the preparation of degradable PEG is here presented.

Synthesis of main chain sulfur-containing aliphatic polycarbonates by organocatalytic ring-opening polymerization of macrocyclic carbonates

The first application of organocatalysts is reported to achieve highly active and living ring-opening polymerization (ROP) of thioether-based macrocyclic carbonates for preparing well-defined main chain thioether functional APCs.

A facile method to prepare high molecular weight bio-renewable poly(γ-butyrolactone) using a strong base/urea binary synergistic catalytic system

Biorenewable poly(γ-butyrolactone) with a high molecular weight was prepared with a base/urea binary synergistic catalyst.

Phosphazene superbase catalyzed ring-opening polymerization of cyclotetrasiloxane toward copolysiloxanes with high diphenyl siloxane content

PDMS-ran-PDPS copolysiloxanes with varying diphenyl siloxane contents (up to 64 mol%) are readily prepared by phosphazene catalyzed ROP.

Fast, selective and metal-free ring-opening polymerization to synthesize polycarbonate/polyester copolymers with high incorporation of ethylene carbonate using an organocatalytic phosphazene base

Polycarbonate/polyester copolymers with high incorporation of EC were realized by a fast and selective process using a metal-free catalyst.

One-Step Access to Sequence-Controlled Block Copolymers by Self-Switchable Organocatalytic Multicomponent Polymerization

A one-step procedure for the self-switchable block copolymerization of monomer mixtures of epoxides, cyclic anhydrides, and lactide (LA) was developed by using simple organocatalysts without an external stimulus. This multicomponent polymerization bridges two catalytic cycles involving ring-opening alternating copolymerization of epoxides with anhydrides and ring-opening polymerization (ROP) of LA, in which the presence/absence of anhydrides in mixed feedstocks switched the ROP of LA off/on. The self-switchable terpolymerization showed distinct noncoordinating and living nature, as well as perfect chemoselectivity. Different combinations of epoxides, anhydrides, and initiators enabled the generation of a variety of new block polyester polyols.

Facile Preparation of Stereoblock PLA From Ring-Opening Polymerization of rac-Lactide by a Synergetic Binary Catalytic System Containing Ureas and Alkoxides

Ring-opening polymerization (ROP) of cyclic esters/lactones by efficient catalysts is a powerful method for synthesis of biodegradable and biocompatible polyesters with well-defined structures. To develop catalytic systems that are fast, selective and controlled is a persistent effort of chemists. In this contribution, we report a binary urea/alkoxide catalytic system that could catalyze ROP of rac-LA in a fast (over 90% conversion within 1-2 min), stereoselective (P i up to 0.93) and controlled manner, indicated by narrow MW distributions, linear relationship between the monomer conversions and M ns, end-group fidelity, and chain extension experiments. Remarkably, the catalytic system described here is simple, easily prepared, and structurally tunable and thus has versatile catalytic performances.

Stereoselective Ring-Opening Polymerization of rac-Lactide Using Organocatalytic Cyclic Trimeric Phosphazene Base

Phosphazene base is an important organocatalyst in polymer chemistry owing to its high activity and versatility. In this contribution, we demonstrate that cyclic trimeric phosphazene base (CTPB) can catalyze stereoselective ring-opening polymerization (ROP) of rac-lactide (rac-LA) to produce isotactic stereoblock PLA (P_i up to 0.93). The polymerizations are highly controlled, as evidenced by linear relationship between molecular weights (MW) and monomer conversions and the narrow dispersity (Đ = M_w/M_n) of the resulted polymers with high fidelity of end groups. The investigations on polymerization parameters show that the tacticity of produced PLA depends on the polymerization temperatures and solvents, while the kinetic studies reveal a faster rate for ROP of l-LA as compared to rac-LA under same conditions. Based on these results, the chain end control mechanism is proposed to explain the production of isotactic stereoblock PLA from rac-LA by an achiral catalyst.

Precise synthesis of sulfur-containing polymers via cooperative dual organocatalysts with high activity

Metal-free and controlled synthesis of sulfur-containing polymer is still a big challenge in polymer chemistry. Here, we report a metal-free, living copolymerization of carbonyl sulfide (COS) with epoxides via the cooperative catalysis of organic Lewis pairs including bases (e.g.: phosphazene, amidine, and guanidine) and thioureas as hydrogen-bond donors, afford well-defined poly(monothiocarbonate)s with 100% alternating degree, >99% tail-to-head content, controlled molecular weights (up to 98.4 kg/mol), and narrow molecular weight distributions (1.13-1.23). The effect of the types of Lewis pairs on the copolymerization of COS with several epoxides is investigated. The turnover frequencies (TOFs) of these Lewis pairs are as high as 112 h-1 at 25 °C. Kinetic and mechanistic results suggest that the supramolecular specific recognition of thiourea to epoxide and base to COS promote the copolymerization cooperatively. This strategy provides commercially available Lewis pairs for metal-free synthesis of sulfur-containing polymers with precise structure.

Schiff base and reductive amination reactions of α-amino acids: a facile route toward N-alkylated amino acids and peptoid synthesis

Polypeptoids are a promising class of peptidomimetic polymers for applications in biotechnology, but the polymers prepared by solution polymerization have limited side-chain functionalities due to synthetic difficulty.

Dynamic diselenide-containing polyesters from alcoholysis/oxidation of γ-butyroselenolactone

A versatile protocol for the synthesis of a variety of multiresponsive diselenide-containing polyesters was investigated.

Polarized olefins as enabling (co)catalysts for the polymerization of γ-butyrolactone

N-Heterocyclic olefins (NHOs) can homopolymerize GBL via anionic or zwitterionic pathways, whereby polymerization mode and polymer topology depend on the chemical structure of the NHO and the presence of LiCl as cocatalyst.

Preparation of biorenewable poly(γ-butyrolactone)-b-poly(l-lactide) diblock copolyesters via one-pot sequential metal-free ring-opening polymerization

Biorenewable block copolyesters were prepared from l-LA and non-polymerizable γBL via a one-pot strategy.

Synthesis of linear and star poly(ε-caprolactone) with controlled and high molecular weights via cyclic trimeric phosphazene base catalyzed ring-opening polymerization

Linear and star PCLs with controlled and high molecular weights are efficiently prepared by a catalytic system of CTPB/alcohol.