Novel thermoplastic elastomers based on multi-block copolymers of poly(l-lysine) (PLL), poly(N-ε-carbobenzyloxyl-l-lysine) (PZLL), poly(ε-caprolactone) (PCL), and poly(ethylene glycol) (PEG) were synthesized by combination of ring-opening polymerization (ROP) and chain extension via l-lysine diisocyanate (LDI). SEC and ¹H NMR were used to characterize the multi-block copolymers, with number-average molecular weights between 38,900 and 73,400 g/mol. Multi-block copolymers were proved to be good thermoplastic elastomers with Young's modulus between 5 and 60 MPa and tensile strain up to 1300%. The PLL-containing multi-block copolymers were electrospun into non-woven mats that exhibited high surface hydrophilicity and wettability. The polypeptide–polyester materials were biocompatible, bio-based and environment-friendly for promising wide applications. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 3012–3018

Unmodified β-cyclodextrin has been directly used to initiate ring-opening polymerization of ϵ-caprolactone in the presence of yttrium trisphenolate. Well-defined cyclodextrin (CD)-centered star-shaped poly(ϵ-caprolactone)s have been successfully synthesized containing definite average numbers of arms (N_arm = 4–6) and narrow polydispersity indexes (below 1.10). The number-average molecular weight () and average molecular weight per arm () are controlled by the feeding molar ratio of monomer to initiator. The prepared star-PCL with of 2.7 × 10³ is in fully amorphous and that with of 13.3 × 10³ is crystallized. In addition, the obtained poly(e-caprolactone) (PCL) stars with various molecular weights have different solubilities in methanol and tetrahydrofuran, which can be applied for further modifications.

In this article, we provide a concept of a two-phase polymerization system consisting of immiscible monomer and room temperature ionic liquid (IL). The catalyst is immobilized in the IL phase where polymerization takes place. The produced polymer is extracted by the monomer, and the remaining IL phase is catalytically active for more polymerizations. Thus, common volatile organic solvents are no longer needed. Ring-opening polymerization of cyclohexene oxide (CHO) in 1-n-butyl-3-methylimidazolium tetrafluoroborate IL ([bmim][BF₄]) using scandium triflate [Sc(OTf)₃] catalyst serves as a realistic example of such concept. The yield of polyCHO in [bmim][BF₄] is higher than that in bulk. IL containing Sc(OTf)₃ can be used for at least three times. A circulatory polymerization process is carried out with added catalyst to keep a relatively high yield in following circulation processes. The assignments of proton signals of polyCHO in ¹H NMR are discussed in detail. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Five rare earth complexes are first introduced to catalyze ring opening polymerizations (ROPs) of γ-benzyl-L-glutamate N-carboxyanhydride (BLG NCA) and L-alanine NCA (ALA NCA) including rare earth isopropoxide (RE(OiPr)₃), rare earth tris(2,6-di-tert-butyl-4-methylphenolate) (RE(OAr)₃), rare earth tris(borohydride) (RE(BH₄)₃(THF)₃), rare earth tris[bis(trimethylsilyl)amide] (RE(NTMS)₃), and rare earth trifluoromethanesulfonate. The first four catalysts exhibit high activities in ROPs producing polypeptides with quantitative yields (>90%) and moderate molecular weight (MW) distributions ranging from 1.2 to 1.6. In RE(BH₄)₃(THF)₃ and RE(NTMS)₃ catalytic systems, MWs of the produced polypeptides can be controlled by feeding ratios of monomer to catalyst, which is in contrast to the systems of RE(OiPr)₃ and RE(OAr)₃ with little controllability over the MWs. End groups of the polypeptides are analyzed by MALDI-TOF MS and polymerization mechanisms are proposed accordingly. With ligands of significant steric hindrance in RE(OiPr)₃ and RE(OAr)₃, deprotonation of 3-NH of NCA is the only initiation mode producing a N-rare earth metallated NCA (i) responsible for further chain growth, resulting in α-carboxylic-ω-aminotelechelic polypeptides after termination. In the case of RE(BH₄)₃(THF)₃ with small ligands, another initiation mode at 5-CO position of NCA takes place simultaneously, resulting in α-hydroxyl-ω-aminotelechelic polypeptides. In RE(NTMS)₃ system, the protonated ligand hexamethyldisilazane (HMDS) initiates the polymerization and produces α-amide-ω-aminotelechelic polypeptides. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

In this work, rare earth tris(borohydride) complexes, Ln(BH₄)₃(THF)₃ (Ln = Sc, Y, La, and Dy), have been used to catalyze the ring-opening polymerization of γ-benzyl-L-glutamate N-carboxyanhydride (BLG NCA). All the catalysts show high activities and the resulting poly(γ-benzyl-L-glutamate)s (PBLGs) are recovered with high yields (≥90%). The molecular weights (MWs) of PBLG can be controlled by the molar ratios of monomer to catalyst, and the MW distributions (MWDs) are relatively narrow (as low as 1.16) depending on the rare earth metals and reaction temperatures. Block copolypeptides can be easily synthesized by the sequential addition of two monomers. The obtained P(γ-benzyl-L-glutamate-b-ε-carbobenzoxy-L-lysine) [P(BLG-b-BLL)] and P(γ-benzyl-L-glutamate-b-alanine) [P(BLG-b-ALA)] have been well characterized by NMR, gel permeation chromatography, and differential scanning calorimetry measurements. A random copolymer P(BLG-co-BLL) with a narrow MWD of 1.07 has also been synthesized. The polymerization mechanisms have been investigated in detail. The results show that both nucleophilic attack at the 5-CO of NCA and deprotonation of 3-NH of NCA in the initiation process take place simultaneously, resulting in two active centers, that is, an yttrium ALA carbamate derivative [H₂BOCH₂(CH)NHC(O)OLn] and a N-yttriumlated ALA NCA. Propagation then proceeds on these centers via both normal monomer insertion and polycondensation. After termination, two kinds of telechelic polypeptide chains, that is, α-hydroxyl-ω-aminotelechelic chains and α-carboxylic-ω-aminotelechelic ones, are formed as characterized by MALDI-TOF MS, ¹H NMR, ¹³C NMR, ¹H–¹H COSY, and ¹H–¹³C HMQC measurements. By decreasing the reaction temperature, the normal monomer insertion pathway can be exclusively selected, forming an unprecedented α-hydroxyl-ω-aminotelechelic polypeptide. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Reaction of yttrium tris[bis(trimethylsilyl)amide] [(TMSN)₃Y] with equivalent L-alanine N-carboxyanhydride (ALA NCA) yields yttrium α-isocyanato carboxylate (II), yttrium ketenyl carbamate (III), and hexamethyldisilazane (V). The products indicate that 4-CH group of ALA NCA monomer is deprotonated in addition to 3-NH group, which has been neglected in NCA chemistry for decades. This result proves the acidity of 4-CH in NCA and provides the first direct evidence for racemization phenomenon of NCA in strong base in microscopic aspect. Rare earth tris[bis(trimethylsilyl)amide] (TMSN)₃Ln (Ln = Sc, Y, La, Dy, and Lu) compounds are high efficient catalysts for ring-opening polymerizations of NCAs. Polypeptides can be produced in quantitative yields with narrow molecular weight distributions below 1.3, and block copolypeptides can be facilely prepared by sequential addition method. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

A new kind of polymeric chemosensor containing chiral naphthaldimine moiety in the side chain was synthesized by the reversible addition-fragmentation chain transfer polymerization of N-{[2-(4-vinylbenzyloxy)-1-naphthyl]-methylene}-(S)-2-phenylglycinol (VNP). The resulting polymers (PVNP) showed high selectivity for hydrogen sulfate relative to other anions including F⁻, Cl⁻, Br⁻, H₂PO, CH₃CO, and NO in tetrahydrofuran (THF) solution as judged from UV−vis, fluorescence, and circular dichroism spectrophotometric titrations. Compared with its monomer, the polymer has proven to be more attractive for detection of HSO in terms of sensitivity and reproducibility. Upon addition of the anion it gives remarkable spectral responses concomitant with detectable color change from colorless to pale yellow. Furthermore, the HSO-induced CD or fluorescence signal can be totally reversed with addition of base and eventually recovered the initial state, leading to a reproducible molecular switch with two distinguished “on” and “off” states. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Although the ring-opening polymerization (ROP) of ε-caprolactone (CL) in toluene at 100 °C can be initiated by yttrium trisphenolate (Y(OC₆H₅)₃), in the presence of 1,2-propanediol (PD) the ROP gives much better, that is, controlled polymerizations. In this case, the molecular weights (MWs) are controlled by the CL/PD molar ratios with primary and secondary hydroxyl groups both initiating the ROP and the MW distributions are narrow. The chain transfers between the active yttrium alkoxides and the residual hydroxyl groups on the PD and/or the chain ends appear to be much faster than chain propagation, consistent with the living character of the ROP. Computational studies support these facile reactions with estimated activation free energies in the 3.0–4.5 kcal/mol range compared with about 25–30 kcal/mol for the polymerization. Intramolecular transfer within the PD is predicted to be negligible having a calculated activation energy of 19 kcal /mol. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Ring-opening polymerization of 1-methyltrimethylene carbonate (MTMC) initiated by highly active single-component rare earth tris(2,6-di-tert-butyl-4-methylphenolate)s [Ln(OAr)₃, Ln = La, Dy, Y] or yttrium isopropoxide [Y(OiPr)₃] is reported for the first time. PolyMTMC (M_w = 8.4 × 10⁴, molecular weight distributions = 1.5) initiated by La(OAr)₃ at [MTMC]/[initiator] = 1000 was obtained with the yield over 99% in toluene within 1 h at 30 °C. Random and block copolymers of MTMC with ε-caprolactone (CL), 2,2-dimethyltrimethylene carbonate (DTC) or polyethylene glycol (PEG) including poly(MTMC-r-CL), poly(MTMC-b-CL), poly(MTMC-r-DTC), poly(MTMC-b-DTC), and poly(MTMC-b-PEG-b-MTMC) were synthesized. The differential scanning calorimetry results show that thermal behaviors of the polymers sensitively depend on their compositions and chain structures. Furthermore, the measurements of ¹H-¹H COSY and density functional theory calculation are applied to investigate the mechanism. The polymerization of MTMC takes place according to a coordination-insertion mechanism, and the ring is opened via acyl-oxygen bond cleavage resulting in a LnO active center. There exist two ring-opening modes of MTMC in which mode b, breaking the CH₂OCO bond, is the major pathway. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3807–3815, 2010