The ring-opening polymerization of δ-valerolactone (δ-VL) and ε-caprolactone (ε-CL) using 3-phenyl-1-propanol (PPA) as the initiator and diphenyl phosphate (DPP) as the catalyst in toluene at room temperature with the [δ-VL or ε-CL]0/[PPA]0/[DPP] ratio of 50/1/1 homogeneously proceeded to afford poly(δ-valerolactone) (PVL) and poly(ε-caprolactone) (PCL) with narrow polydispersity indices. The molecular weights determined from a 1H NMR analysis (PVL, M n,NMR = 5170 g mol−1 and PCL, M n,NMR = 5920 g mol−1) showed good agreement with those estimated from the initial ratio of [δ-VL or ε-CL]0/[PPA]0 and monomer conversions (PVL, M n,theo = 4890 g mol−1 and PCL, M n,theo = 5680 g mol−1). The 1H NMR, SEC, and MALDI-TOF MS measurements of the obtained PVL and PCL clearly indicated the presence of the initiator residue at the chain end, confirming that the DPP-catalyzed ROP of lactones proceeded through an activated monomer mechanism. The kinetic and chain extension experiments confirmed the controlled/living nature for the DPP-catalyzed ROP of lactones. In addition, the block copolymerization of PVL and PCL successfully proceeded to afford PVL-b-PCL regardless of the monomer addition sequence. The DPP-catalyzed ROP of δ-VL and ε-CL using functional initiators, such as 2-hydroxyethyl methacrylate, 4-vinylbenzyl alcohol, propargyl alcohol, and 6-azido-1-hexanol, produced the corresponding end-functionalized PVLs and PCLs with narrow molecular weight distributions.

The ring-opening polymerization (ROP) of cyclic carbonates with diphenyl phosphate (DPP) as the organocatalyst and 3-phenyl-1-propanol (PPA) as the initiator has been studied using trimethylene carbonate (TMC), 5,5-dimethyl-1,3-dioxan-2-one, 5,5-dibromomethyl-1,3-dioxan-2-one, 5-benzyloxy-1,3-dioxan-2-one, 5-methyl-5-allyloxycarbonyl-1,3-dioxan-2-one, and 5-methyl-5-propargyloxycarbonyl-1,3-dioxan-2-one. All the polymerizations proceeded without backbiting, decarboxylation, and transesterification reactions to afford polycarbonates having narrow polydispersity indices. In addition, 6-azido-1-hexanol, propargyl alcohol, and N-(2-hydroxyethyl)maleimide were used as functional initiators for the DPP-catalyzed ROP to produce the end-functionalized poly(trimethylene carbonate)s. For further modification of the azido end-functionlized polycarbonate, the macrocyclic poly(trimethylene carbonate) was synthesized by the intramolecular click cyclization of the α-azido, ω-ethynyl poly(trimethylene carbonate). The DPP-catalyzed ROP was applicable for the block copolymerization of TMC and δ-valerolactone or ε-caprolactone to afford poly(trimethylene carbonate)-block-poly(δ-valerolactone) and poly(trimethylene carbonate)-block-poly(ε-caprolactone), and for that of TMC and l-lactide using DPP coupled with 4-dimethylaminopyridine without quenching to produce poly(trimethylene carbonate)-block-poly(l-lactide).

For the living ring‐opening polymerization (ROP) of epoxy monomers, the catalytic activity of organic superbases, tert‐butylimino‐tris(dimethylamino)phosphorane, 1‐tert‐butyl‐2,2,4,4,4‐pentakis(dimethylamino)‐2Λ5,4Λ5‐catenadi(phosphazene), 2,8,9‐triisobutyl‐2,5,8,9‐tetraaza‐1‐phosphabicyclo[3.3.3]undecane, and 1‐tert‐butyl‐4,4,4‐tris(dimethylamino)‐2,2‐bis[tris(dimethylamino)phosphoranylidenamino]‐2Λ5,4Λ5‐catenadi(phosphazene) (t‐Bu‐P4), was confirmed. Among these superbases, only t‐Bu‐P4 showed catalytic activity for the ROP of 1,2‐butylene oxide (BO) to afford poly(1,2‐butylene oxide) (PBO) with predicted molecular weight and narrow molecular weight distribution. The results of the kinetic, post‐polymerization experiments, and MALDI‐TOF MS measurement revealed that the t‐Bu‐P4‐catalyzed ROP of BO proceeded in a living manner in which the alcohol acted as the initiator. This alcohol/t‐Bu‐P4 system was applicable to the glycidol derivatives, such as benzyl glycidyl ether (BnGE) and t‐butyl glycidyl ether, to afford well‐defined protected polyglycidols. The α‐functionalized polyethers could be obtained using different functionalized initiators, such as 4‐vinylbenzyl alcohol, 5‐hexen‐1‐ol, and 6‐azide‐1‐hexanol. In addition, the well‐defined cyclic‐PBO and PBnGE were successfully synthesized using the combination of t‐Bu‐P4‐catalyzed ROP and click cyclization. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

A high enantiomer-selectivity for the polymerization of rac-lactide was achieved using chiral binaphthol-derived monophosphoric acids as organocatalysts. During the polymerization, d-lactide (DLA) preferentially polymerized via kinetic resolution with the maximum selectivity factor (kD/kL) of 28.3. The selective polymerization of DLA was derived from a dual activation, i.e., monomer activation and chain-end activation.

The ring-opening polymerizations (ROPs) of e-caprolactone (e-CL) and L-lactide (LLA) have been studied using the organocatalysts of diphenyl phosphate (DPP) and 4dimethylaminopyridine (DMAP). The "dual activation" property of DPP and the "bifunctional activation" property of DPP/DMAP were confirmed by the NMR measurement for e-CL and its chain-end model of poly(e-caprolactone) and for LLA and its chain-end model of poly(L-lactide) (PLLA), respectively. The molar ratio of DPP/DMAP was optimized as 1/2 for the ROP of LLA leading to the well-defined PLLA, such as the molecular weight determined from 1 H NMR measurement of 19,200 g mol 21 and the narrow polydispersity of 1.10. Additionally, functional initiators were utilized for producing the end-functionalized PLLAs. The DPP-catalyzed ROPs of e-CL and its analogue cyclic monomers and then the DPP/DMAP-catalyzed ROP of LLA produced block copolymers.

The ring-opening polymerization (ROP) of bbutyrolactone (b-BL) has been studied using the organocatalysts of diphenyl phosphate (DPP) and bis(4-nitrophenyl) phosphate (BNPP). The controlled ROP of b-BL was achieved using BNPP, whereas that of using DPP was insufficient because of its low acidity. For the BNPP-catalyzed ROP of b-BL, the dual activation property for b-BL and the chain-end models of poly(b-butyrolactone) (PBL) were confirmed by NMR measurements. The optimized polymerization condition for the ROP of b-BL proceeded through an O-acyl cleavage to produce the well-defined PBLs with molecular weights up to 10,650 g mol 21 and relatively narrow polydispersities of 1.19-1.39. Func-tional initiators were utilized for producing the endfunctionalized PBLs with the ethynyl, maleimide, pentafluorophenyl, methacryloyl, and styryl groups. Additionally, the diblock copolymers consisting of the PBL segment with the polyester or polycarbonate segments were prepared by the BNPP-catalyzed ROPs of e-caprolactone or trimethylene carbonate without quenching.

The ring‐opening polymerization (ROP) of cyclic esters, such as ε‐caprolactone, 1,5‐dioxepan‐2‐one, and racemic lactide using the combination of 3‐phenyl‐1‐propanol as the initiator and triflimide (HNTf2) as the catalyst at room temperature with the [monomer]0/[initiator]0 ratio of 50/1 was investigated. The polymerizations homogeneously proceeded to afford poly(ε‐caprolactone) (PCL), poly(1,5‐dioxepan‐2‐one) (PDXO), and polylactide (PLA) with controlled molecular weights and narrow polydispersity indices. The molecular weight determined from an 1H NMR analysis (PCL, Mn,NMR = 5380; PDXO, Mn,NMR = 5820; PLA, Mn,NMR = 6490) showed good agreement with the calculated values. The 1H NMR and matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry analyses strongly indicated that the obtained compounds were the desired polyesters. The kinetic measurements confirmed the controlled/living nature for the HNTf2‐catalyzed ROP of cyclic esters. A series of functional alcohols, such as propargyl alcohol, 6‐azido‐1‐hexanol, N‐(2‐hydroxyethyl)maleimide, 5‐hexen‐1‐ol, and 2‐hydroxyethyl methacrylate, successfully produced end‐functionalized polyesters. In addition, poly(ethylene glycol)‐block‐polyester, poly(δ‐valerolactone)‐block‐poly(ε‐caprolactone), and poly(ε‐caprolactone)‐block‐polylactide were synthesized using the HNTf2‐catalyzed ROP. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2455–2463

The ring‐opening polymerizations (ROPs) of ε‐caprolactone (ε‐CL) and δ‐valerolactone (δ‐VL) with pentafluorophenylbis(triflyl)methane (C6F5CHTf2) as the organocatalyst and alcohol initiators were carried out. For the ROP using 3‐phenyl‐1‐propanol (PPA) as the initiator in CH2Cl2 at room temperature with the [ε‐CL or δ‐VL]0/[PPA]0/[C6F5CHTf2] ratio of 50/1/0.1, the polymerization homogeneously proceeded to afford poly(ε‐caprolactone) (PCL) and poly(δ‐valerolactone) (PVL) having narrow polydispersity indices. The molecular weights of the obtained polymers determined from 1H NMR spectra showed good agreement with those estimated from the initial ratio of [ε‐CL or δ‐VL]0/[PPA]0 and monomer conversions. The 1H NMR, size exclusion chromatography, and matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry measurements strongly indicated that PCL and PVL possessed the 3‐phenylpropoxy group as the α‐chain‐end and the hydroxy group as the ω‐chain‐end. In addition, the controlled/living nature for the C6F5CHTf2‐catalyzed ROP of lactones was confirmed by kinetic and chain‐extension experiments. The block copolymerization of PCL and PVL successfully proceeded to afford PCL‐b‐PVL and PVL‐b‐PCL. In addition, various end‐functionalized PCLs and PVLs with narrow molecular weight distributions were synthesized by the ROP of ε‐CL and δ‐VL using functional initiators, such as 6‐azido‐1‐hexanol, 2‐hydroxyethyl methacrylate, propargyl alcohol, N‐(2‐hydroxyethyl)maleimide, 4‐vinylbenzyl alcohol, 5‐hexen‐1‐ol, and 5‐norbornene‐2‐methanol. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011