Novel drug-conjugated amphiphilic A(14)B(7) miktoarm star copolymers composed of 14 poly(epsilon-caprolactone) (PCL) arms and 7 poly(ethylene glycol) (PEG) arms with beta-cyclodextrin (beta-CD) as core moiety were synthesized by the combination of controlled ring-opening polymerization (CROP) and "click" chemistry. (1)H NMR, FT-IR, and SEC-MALLS analyses confirmed the well-defined A(14)B(7) miktoarm star architecture. These amphiphilic miktoarm star copolymers could self-assemble into multimorphological aggregates in aqueous solution, which were characterized by dynamic light scattering (DLS) and transmission electron microscopy (TEM). Moreover, the drug-loading efficiency and drug-encapsulation efficiency of the drug-conjugated miktoarm star copolymers were higher than those of the corresponding non-drug-conjugated miktoarm star copolymers.

N-substituted glycine N-thiocarboxyanhydrides (NTAs) are alternative monomers to prepare polypeptoids with large-scale producing potential compared to the corresponding N-carboxyanhydrides (NCAs) due to their easily synthetic approach and stability during purification and storage. Novel monomer N-butylglycine NTA (NBG-NTA) has been synthesized and well characterized for the first time. Rare earth borohydrides [RE(BH 4 ) 3 (THF) 3 , RE = Sc, Y, La, Nd, Dy, and Lu] have been first applied in the polymerization of sarcosine NTA (Sar-NTA) and NBG-NTA to achieve high molecular weight (MW) hydrophilic and hydrophobic polypeptoids. Polysarcosines (PSars), poly(N-butylglycine)s (PNBGs), and their copolymers with high yields, high MWs, and moderate MW distributions are synthesized at 60 °C by using RE(BH 4 ) 3 (THF) 3 initiators. MWs of polypeptoids are controlled by feed molar ratios. For instance, PSar with an absolute M n of 27.7 kDa (DP = 390) and PDI of 1.14 is produced successfully from Sar-NTA. Thermoresponsive random copolypeptoids poly(sarcosine-r-N-butylglycine)s [P(Sar-r-NBG)s] have reversible phase transitions (cloud point temperature) in aqueous solution and minimal cytotoxicity comparable to PEG and PSar, which is promising in various biomedical and biotechnological applications. Thermal properties of homo-and co-polypeptoids are investigated by TGA and DSC measurements.

The ring-opening polymerization of 2,2-dimethyltrimethylene carbonate (DTC) initiated with highly active single rare earth tris(2,6-di-tert-butyl-4-methylphenolate) (Ln(OAr)3, Ln = La, Nd, Dy, Y) is reported for the first time. The catalytic activities of various Ln(OAr)3 systems are decreasing in the following sequence:  La > Nd > Dy ∼ Y. PolyDTC (M w = 17.1 × 104, MWD = 2.79) initiated by La(OAr)3 at [DTC]/[initiator] = 1000 was obtained with a conversion of 97.9% within 1 h in toluene at 15 °C. 1H NMR, GPC, and DSC are used to characterize the polymer's structure and to investigate the polymerization mechanism. PolyDTC obtained has no ether unit developed from CO2 elimination. The polymerization of DTC occurs according to a coordination anionic mechanism, and the ring is opened via acyl−oxygen cleavage leading to an Ln−O active center.

The steric effect of bulky groups of the catalyst can kinetically suppress the transesterification reactions by screening linear polymer chains from the active center during the polymerization of ε-caprolactone (CL) with rare earth alkoxide. Therefore, isopropoxy rare earth diethyl acetoacetate ((EA)2LnOiPr Ln = Nd, Y) and Nd(OiPr)3-donor adducts (1,10-phenanthroline, 2,2‘-bipyridyl, 18-crown-6 ether) are excellent catalysts for the living polymerization of ε-caprolactone, giving poly(ε-caprolactone) (PCL) with a narrow molecular weight distribution. Block copolymerizations of ε-caprolactone with trimethylene carbonate (TMC) and d,l-lactide (LA) have been attained successfully using (EA)2LnOiPr as catalyst. The characterizations by GPC, NMR, DSC, and polarizing microscope showed that the block copolymers, P(CL-b-TMC) and P(CL-b-d,l-lactide), have well-controlled sequences without random placement.

Biobased and environmental-friendly polylactones provide a solution to the increasing crisis of fossilsourced products. Ring-opening polymerization (ROP) of ε-decalactone (DL) catalyzed by lanthanum tris(2,6-di-tert-butyl-4-methylphenolate) [La(OAr) 3 ] and lanthanum tris-(borohydride) [La(BH 4 ) 3 (THF) 3 ] is reported for the first time in this paper. Both of them exhibit good activities producing poly(ε-decalactone) (PDL) with molecular weight (MW) up to 26.4 kg/mol and polydispersity index (PDI) as low as 1.10. PLLA-b-PDL-b-PEG-b-PDL-b-PLLA pentablock copolymers with predictable MWs and relatively narrow PDIs (1.19−1.28) are synthesized by sequential ROP of DL and Llactide (LLA) catalyzed by La(OAr) 3 in the presence of poly(ethylene glycol) (PEG). Chain extension reactions of the obtained pentablock copolymers are carried out using L-lysine diisocyanate (LDI) to produce multiblock copolymers with relatively high MW. The thermal behaviors studied by DSC and DMA measurements indicate that PDL is completely amorphous under ambient temperature and the copolymers with two T g s suggest microphase separation of hard and soft domains. We employ tensile tests to assess mechanical properties and find excellent elongation up to 723% of the chain-extended samples. Considering the biorenewable resource of DL and LLA, a novel, biobased, biodegradable, and biocompatible elastomer is successfully synthesized.

Copolymers of -caprolactone (CL) and trimethylene carbonate (TMC) have been synthesized through ring-opening polymerization using a novel initiator of scandium tris(2,6-di-tert-butyl-4-methylphenolate). CL and TMC polymerizations proceed via the "coordination anionic mechanism" with acyloxygen bond cleavage. Five kinds of copolymers with different structures of X, XB, AXB, AB, and BAXB are synthesized under different polymerization conditions and characterized by 1 H NMR, GPC, and DSC, where X, A, and B denote as random blocks of CL and TMC, PTMC blocks, and PCL blocks, respectively.

No abstract

Highly random copolymers of ϵ‐caprolactone (CL) and D,L‐lactide (LA) were synthesized by a new catalyst system, rare earth chloride–propylene oxide (PO) system. In the presence of propylene oxide, all rare earth chlorides tested are highly effective for the copolymerization. The influences of reaction conditions on the copolymerization catalyzed by the NdCl3‐5PO system have been investigated in detail. The reactivity ratios of ϵ‐caprolactone and D,L‐lactide were determined and show that the copolymerization with this new rare earth catalyst is closer to ideal copolymerization than reported for other catalysts. The microstructure of copolymer analyzed by 13C‐NMR shows that the monomer units in the copolymer is near to completely random distribution with a short average monomer sequence length. The DSC measurement confirms the high randomness of the chain structure. The mechanism studied by NMR indicates that the rare earth alkoxide generated by the reaction of rare earth chloride with propylene oxide initiates the copolymerization, and then proceeds via a “coordination‐insertion” mechanism with acyl‐oxygen bond cleavage of CL and LA. © 1996 John Wiley & Sons, Inc.