Phosphazene Functionalized Silsesquioxane-Based Porous Polymer as Thermally Stable and Reusable Catalyst for Bulk Ring-Opening Polymerization of ε-Caprolactone

The bulk ring-opening polymerization (ROP) of ε-caprolactone using phosphazene-containing porous polymeric material (HPCP) has been studied at high reaction temperatures (130-150 °C). HPCP in conjunction with benzyl alcohol as an initiator induced the living ROP of ε-caprolactone, affording polyesters with a controlled molecular weight up to 6000 g mol^-1 and moderate polydispersity (Ð~1.5) under optimized conditions ([BnOH]/[CL] = 50; HPCP: 0.63 mM; 150 °C). Poly(ε-caprolactone)s with higher molecular weight (up to M_n = 14,000 g mol^-1, Ð~1.9) were obtained at a lower temperature, at 130 °C. Due to its high thermal and chemical stability, HPCP can be reused for at least three consecutive cycles without a significant decrease in the catalyst efficiency. The tentative mechanism of the HPCP-catalyzed ROP of ε-caprolactone, the key stage of which consists of the activation of the initiator through the basic sites of the catalyst, was proposed.

Ultrafast ring-opening copolymerization of lactide with glycolide toward random poly(lactic-co-glycolic acid) copolymers by organophosphazene base and urea binary catalysts

The preparation of poly(lactic-co-glycolic acid) (PLGA) copolymers with controllable random microstructures remains as a challenge due to the much higher reactivity of glycolide (GA) compared to lactide (LA). In this...

Synthesis of Diverse Polycarbonates by Organocatalytic Copolymerization of CO2 and Epoxides: From High Pressure and Temperature to Ambient Conditions

Organophosphazenes combined with triethylborane (TEB) were selected as binary organocatalyts for the copolymerization of CO₂ and epoxides. Both the activity and selectivity were highly dependent on the nature of phosphazenes. 2,4,6-Tris[tri(1-pyrrolidinyl)-iminophosphorane]-1,3,5-triazine (C₃ N₃ -Py-P₃ ) with a relatively low basicity (pK_a =26.5 in CD₃ CN) and a bulky molecular size (φ=1.3 nm) exhibited an unprecedented efficiency (TON up to 12240) and selectivity (>99 % polymer selectivity and >99 % carbonate linkages) toward copolymerization of CO₂ and cyclohexene oxide (CHO), and produced CO₂ -based polycarbonates (CO₂ -PCs) with high molar masses (M_n up to 275.5 kDa) at 1 MPa of CO₂ and 80 °C. Surprisingly, this binary catalytic system achieved efficient CO₂ /CHO copolymerization with TOF up to 95 h^-1 at 1 atm pressure and room temperature.

Facile fabrication of a controlled polymer brush-type functional nanoprobe for highly sensitive determination of alpha fetoprotein

As robust functional polymers, polymer brush-based hybrid nanomaterials have potential application in the highly sensitive determination of tumor markers (TMs). Currently, there are plentiful reports on the polymerization methods of functional polymer brushes. Low ppm ATRP (activators (re)generated by electron transfer for atom transfer radical polymerization (A(R)GET ATRP), initiators for continuous activator regeneration atom transfer radical polymerization (ICAR ATRP) and electrochemically mediated atom transfer radical polymerization (eATRP)) is a facile and robust methodology with the advantages of simplicity, eco-friendliness and wide applicability to prepare well-defined polymeric materials. In this work, a controlled polymer brush-type functional nanoprobe is successfully fabricated by functional AGET ATRP and used as a sandwich-type electrochemical immunosensor for precise detection of TMs (alpha-fetoprotein, AFP). Using graphene oxide (GO) as an excellent conductive matrix, a GO-based poly-heterozygosis pyridine nanomaterial (GO@PHPY) is obtained by surface-initiated AGET ATRP and photocatalytic modification. The nanoprobe is assembled using GO@PHPY and a detection antibody (Ab2) to detect AFP, in which Cu(ii) serves as a signal label to coordinate with the pyridyl group. Under optimized conditions, the electrochemical sensor exhibits a good detection effect on AFP, with a detection range of 0.1 pg mL^-1 to 100 ng mL^-1 and a low detection limit of 0.08 pg mL^-1. It is worth noting that the detection platform can be applied to the detection of real human serum samples. Thus, it is a desirable platform for AFP detection in clinical diagnosis and practical applications. Meanwhile, this work proves that designing and constructing functional polymer brushes is one of the most effective methods for developing new materials for analytical scientific applications.

Organoselenium chemistry-based polymer synthesis

Novel synthesis of selenium containing polymers with pre-determined structures and applications thereof.

Chiral phosphoric acid catalyzed asymmetric kinetic resolution polymerization of 6-aryl-ε-caprolactones

The first chiral phosphoric acid catalyzed asymmetric kinetic resolution polymerization (AKRP) of 6-aryl-ε-caprolactones has been achieved.

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.

High Performance Quantification of Complex High Resolution Polymer Mass Spectra

Modern soft ionization mass spectrometry provides chemical information on various polymers with unparalleled resolution and sensitivity. However, the interpretation of the resulting highly complex mass spectra is hampered by the sheer amount of contributing macromolecular species. For example, state-of-the-art reversible deactivation radical polymerization techniques, which are generally considered to be highly controlled, can still generate tens or even hundreds of species in a narrow mass window. Moreover, the multitude of species typically leads to partially overlapping isotopic patterns, further complicating the data evaluation. Herein, a rapid and powerful three-step methodical approach is introduced that enables the successful identification and quantification of the contributing species. The approach is subsequently implemented in "pyMacroMS", a high performance algorithm that allows for ultrafast processing of high resolution polymer mass spectra with varying complexities. The power of our algorithm is demonstrated on the example of a photochemical atom transfer radical polymerization (photoATRP) of three monomers, ultimately leading to 908 identified species. pyMacroMS is available free of charge under a GNU General Public License v3.0.

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.

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.