Sequential polymerization of ethylene oxide, ε-caprolactone and l-lactide: a one-pot metal-free route to tri- and pentablock terpolymers

Triblock and pentablock terpolymers are prepared via one-pot sequential polymerization of ethylene oxide, ε-caprolactone and l-lactide using a mild phosphazene base as an organic catalyst and monoalcohol or water as an initiator.

2,4-Dinitrobenzenesulfonic acid in an efficient Brønsted acid-catalyzed controlled/living ring-opening polymerization of ε-caprolactone

2,4-Dinitrobenzenesulfonic acid as an efficient Brønsted acidic catalyst has been evaluated for the controlled/living ring-opening polymerization of ε-caprolactone end-functionalized, α,ω-dihydroxy telechelic poly(ε-caprolactone), and diblock copolymers were also synthesised successfully.

Chemically modifiable N-heterocycle-functionalized polycarbonates as a platform for diverse smart biomimetic nanomaterials

A series of aliphatic polycarbonates bearing pendant N-heterocycles serves as a common platform towards diverse biodegradable nanomaterials.

Phosphazene-catalyzed ring-opening polymerization of ε-caprolactone: influence of solvents and initiators

Metal-free ring-opening polymerization of ε-caprolactone was conducted using a relatively mild phosphazene base catalyst. The influence of solvents and protic initiators on the polymerization rate and control was demonstrated.

Enantiopure N,N,O-scorpionate zinc amide and chloride complexes as efficient initiators for the heteroselective ROP of cyclic esters

Amide-containing zinc heteroscorpionates can act as single-component initiators for the well-controlled ROP of rac-LA to produce heterotactic-enriched materials.

Bis(phosphinoselenoic amides) as versatile chelating ligands for alkaline earth metal (Mg, Ca, Sr and Ba) complexes: syntheses, structure and ε-caprolactone polymerisation

A series of alkaline earth metal (Mg, Ca, Sr, Ba) complexes with the bis(phosphinoselenoic amine) ligand have been reported and the complexes are utilized as catalysts for the ROP of ε-caprolactone.

‘Immortal’ ring-opening polymerization of ω-pentadecalactone by Mg(BHT)2(THF)2

The ‘immortal’ ring-opening polymerization (iROP) of pentadecalactone (PDL), catalysed by magnesium 2,6-di-tert-butyl-4-methylphenoxide (Mg(BHT)₂(THF)₂) under non-inert conditions is reported for the first time.

Chiral lanthanide complexes: coordination chemistry, spectroscopy, and catalysis

Luminescent lanthanide complexes bearing amido-bisoxazoline ligands are reported. They were studied using time-resolved luminescence spectroscopy, and were probed for their activity in hydroamination/cyclisation and ring-opening polymerisation catalysis.

Surface grafted poly(ε-caprolactone) prepared using organocatalysed ring-opening polymerisation followed by SI-ATRP

The controlled ring-opening polymerisation (ROP) of an ATRP initiator-containing lactone, γ-BMPCL, and its copolymerisation with ε-caprolactone is reported. One resulting copolymer was successfully used as a substrate for surface initiated ATRP to produce surface-grafted poly(oligo(ethylene glycol) methacrylate) brushes.

Tetra-n-butylammonium Fluoride as an Efficient Transesterification Catalyst for Functionalizing Cyclic Carbonates and Aliphatic Polycarbonates

We have developed a general method for the functionalization of cyclic carbonate monomers having a pentafluorophenyl ester substituent at the 5-position (MTC-OC₆F₅), as well as the postpolymerization modification of the subsequent polymer, poly(MTC-OC₆F₅), with alcohols. The transesterifications are achieved under mild conditions using catalytic tetra-n-butylammonium fluoride (TBAF) as the nucleophilic acyl transfer agent. As an organic-soluble form of fluoride, TBAF loadings as low as 5 mol % were sufficient in bringing about high conversions at room temperature. The mild reaction conditions preserved the integrity of the sensitive carbonate moieties even without the use of Schlenk techniques. In addition to commercial TBAF solutions, we also found solid-supported forms of TBAF to be effective for transesterification, thus enabling facile postreaction workup and purification. More importantly, with only minor adjustments to the reaction conditions, we show that TBAF also promotes the postpolymerization modification of poly(MTC-OC₆F₅), whereby fluoride-mediated transesterification with various alcohols proceeded quantitatively across the pendant pentafluorophenyl esters. Synthesizing a series of pendant ester-functionalized polycarbonates from a common precursor polymer was previously unattainable with existing methods, an issue that is now resolved by the current work.

One-Step Synthesis of Cross-Linked Block Polymer Precursor to a Nanoporous Thermoset

Using a simultaneous block polymerization/in situ cross-linking from a heterofunctional initiator approach, we produced a nanostructured and cross-linked block polymer in a single step from a ternary mixture of monomers and used it as a precursor for a cross-linked nanoporous material. Using 2-(benzylsulfanylthiocarbonylsulfanyl)ethanol as a heterofunctional initiator, simultaneous ring-opening transesterification polymerization of d,l-lactide in the presence of tin 2-ethylhexanoate as a catalyst and reversible addition-fragmentation chain transfer polymerization of styrene at 120 °C produced a polylactide-b-polystyrene (PLA-b-PS) block polymer. Incorporation of divinylbenzene in the polymerization mixture allowed in situ cross-linking during the simultaneous block polymerization to result in the cross-linked block polymer precursor in one step. This material was converted into cross-linked nanoporous polymer by etching PLA in a basic solution.

Ring opening polymerization of rac-lactide by group 4 tetracarbamato complexes: activation, propagation and role of the metal

A series of group 4 metal tetracarbamates M(O(2)CNR(2))(4) (M = Ti, R = Et, 1a; M = Zr, R = Et, 1b; (i)Pr, 1c; M = Hf, R = Et, 1d; R = (i)Pr, 1e) were studied as catalytic precursors in the solution polymerization of rac-lactide. The titanium complex but not the zirconium and hafnium ones increase the activity by addition of (i)PrOH. The structure of the carbamato ligand markedly influences the molar mass of polymer; the complexes with isopropyl carbamato ligands produced PLA with molar masses up to 94,000 g mol(-1). The main mechanistic aspects of the initial stages of the polymerization reactions were outlined by spectroscopic and computational analyses. In the case of zirconium and hafnium complexes, an interaction between a carbamato ligand and the CH unit of one lactide molecule is established at room temperature. This interaction is followed by the high temperature proton transfer from the lactide to the carbamato O-atom, affording a catalytic active alkoxy complex with release of CO(2) and NHR(2). The polymerization mediated by Ti(O(2)CNEt(2))(4) involves the release of a radical fragment [O(2)CNEt(2)]˙, with consequent generation of a Ti(III) center. The propagating chain is an alcoholate ligand coordinated to a Ti(IV) centre and containing a radical mainly localized at the tail of the chain (DFT, EPR).

Synthesis of Poly(lactide)s with Modified Thermal and Mechanical Properties

The use of poly(lactide)-based materials is, in part, limited by their physical and mechanical properties. This article reviews the methods that have been employed to enable enhancement of the materials properties through synthetic manipulation of the polymer structure including block copolymer synthesis and modification of the lactide monomer structure, focusing on the application of ring-opening polymerization. In turn the effect of these structural modifications on the properties of the resultant materials are reported.