Ring-opening Polymerization Of Δ-valerolactone Research Articles

Ring-opening Copolymerization of ε-Caprolactone and δ-Valerolactone Catalyzed by a 2,6-Bis(amino)phenol Zinc Complex

In combination with methyllithium, a 2,6-bis(amino)phenol zinc complex 1 was used in the ring-opening polymerization of δ-valerolactone in the absence or presence of benzyl alcohol and showed high efficiency, mainly producing cyclic and linear polyvalerolactones, respectively. On the basis of homopolymerization, the ring-opening copolymerization of e-caprolactone and δ-valerolactone was investigated. The P(CL-co-VL) random copolymers, PCL-b-PVL and PVL-b-PCL diblock copolymers, were prepared by varying the feeding strategy (premixing or sequential feeding). The copolymer composition was adjusted by varying the feeding ratio of two monomers. The structure and thermal properties of obtained polymers were characterized by GPC, 1H-NMR, 13C-NMR, MALDI-TOF mass spectroscopy, and DSC, respectively.

Turning on ROP activity in a bimetallic Co/Zn complex supported by a [2+2] Schiff-base macrocycle.

Homo-dinuclear Co and Zn complexes derived from the macrocycle LH2, {[2-(OH)-5-(R)-C6H2-1,3-(CH)2][CH2CH2(2-C6H4N)2]}2 (R = Me, tBu), revealed near inactivity for the ring opening polymerization (ROP) of the cyclic esters δ-valerolactone (δ-VL) and ε-caprolactone (ε-CL). By contrast, the hetero-bimetallic complexes [LCo(NCMe)(μ-Br)ZnBr]·nMeCN (n = 3 or 3.25) were found to be efficient catalysts for the ROP of ε-CL and δ-VL.

In situ gelling polyvalerolactone-based thermosensitive hydrogel for sustained drug delivery

Biodegradable poly(ethyleneglycol)–poly(valerolactone)–poly(ethyleneglycol) [PEG–PVL–PEG] copolymers were synthesized through ring opening polymerization of δ-valerolactone (VL) followed by the coupling of monomethoxy poly(ethyleneglycol–poly(valerolactone) (mPEG–PVL) with hexamethylene diisocyanate (HDI). The copolymers were characterized by 1H NMR, FT-IR, and GPC. Block copolymers of PEG and PVL with different VL/PEG molar ratios were successfully synthesized. One of the copolymers (Copolymer 2, PEG550–PVL6768–PEG550) displayed a sol–gel transition at a physiological temperature based on the test tube inverting method and rheological studies. The thermogelling copolymer demonstrated a characteristic crystalline peak for PVL block as determined by DSC and XRD analysis. In vitro release from the copolymer hydrogel matrix indicated that dexamethasone (DEX), a hydrophobic model drug, released comparatively slower than 5-fluoruracil (5-FU), a hydrophilic model drug, due to the potential partitioning of DEX into the PVL core. 5-FU in vitro release from copolymer 2 was 86% in 22h, whereas only 14% of DEX was released in 24h. Cell viability studies confirmed that hydrogels composed of block copolymers are biocompatible. Copolymer 2 showed more than 80% relative cell viability at all concentrations, including concentrations greater than 200 fold CMC. In vivo gel formation studies indicate that gel integrity was maintained for 7days upon subcutaneous injection into mice. These results indicate that PEG–PVL–PEG copolymers are suitable for drug delivery applications.

O-Benzenedisulfonimide as a recyclable cationic organocatalyst for the controlled/living ring-opening polymerization of δ-valerolactone and ε-caprolactone

A safe, recyclable, and water-tolerant Brønsted acid o-benzenedisulfonimide (OBS) catalyzed ROP of lactones in a living/controlled manner.

Diphenyl Phosphate as an Efficient Cationic Organocatalyst for Controlled/Living Ring-Opening Polymerization of δ-Valerolactone and ε-Caprolactone

The ring-opening polymerization of δ-valerolactone (δ-VL) and e-caprolactone (e-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 e-CL]0/[PPA]0/[DPP] ratio of 50/1/1 homogeneously proceeded to afford poly(δ-valerolactone) (PVL) and poly(e-caprolactone) (PCL) with narrow polydispersity indices. The molecular weights determined from a 1H NMR analysis (PVL, Mn,NMR = 5170 g mol−1 and PCL, Mn,NMR = 5920 g mol−1) showed good agreement with those estimated from the initial ratio of [δ-VL or e-CL]0/[PPA]0 and monomer conversions (PVL, Mn,theo = 4890 g mol−1 and PCL, Mn,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 f...

Controlled/Living Ring-Opening Polymerization of δ-Valerolactone Using Triflylimide as an Efficient Cationic Organocatalyst

The polymerization of δ-valerolactone (δ-VL) using 3-phenyl-1-propanol (3-Ph-PrOH) as the initiator and trifluoromethanesulfonimide (HNTf2) as the catalyst in CH2Cl2 at 27 °C with the [δ-VL]0/[3-Ph-PrOH]0/[HNTf2]0 ratio of 100:1:0.1 proceeded homogeneously to afford a poly(δ-valerolactone) (PVL) with a narrow polydispersity index. The molecular weight determined from the 1H NMR analysis, Mn = 9600 g mol−1, fairly agreed with that estimated from the initial ratio of [δ-VL]0/[3-Ph-PrOH]0, Mn,theo = 9400 g mol−1. In addition, the kinetic and chain extension experiments confirmed that the HNTf2-catalyzed ROP proceeded in a living fashion. The 1H NMR, SEC, and MALDI-TOF MS measurements of the obtained PVL clearly indicated the presence of the initiator residue at the chain end, showing that the HNTf2-catalyzed ROP of δ-VL proceeded through a living mechanism. The HNTf2-catalyzed ROP of δ-VL with functional initiators, such as 6-azido-1-hexanol, 2,3,4,5,6-pentafluorobenzyl alcohol, and N-(2-hydroxyethyl)maleimide, successfully afforded the corresponding end-functionalized PVL with a precise molecular control.

Methoxy poly(ethylene glycol)- b-poly(valerolactone) diblock polymeric micelles for enhanced encapsulation and protection of camptothecin

Amphiphilic block copolymers, methoxy poly(ethylene glycol)- b-poly(valerolactone) (mPEG- b-PVL), were synthesized via ring opening polymerization of δ-valerolactone in the presence of methoxy poly(ethylene glycol) (mPEG). The copolymers form micelle-like nanoparticles by their amphiphilic characteristics and their structures were examined by Nuclear Magnetic Resonance (NMR). The sizes of nanoparticles ranged from 60 to 120 nm as measured by dynamic light scattering detection, and were larger with higher molecular weight of the copolymers. The Critical Micelle Concentration (CMC) of these nanoparticles in water decreased with increasing molecular weight of hydrophobic segment. Stability analysis showed that the micellar solutions maintain their sizes at 37 °C for six weeks without aggregation or dissociation. The lyophilization method was better than the evaporation method when camptothecin (CPT) was incorporated to the micelles. The former method yielded higher CPT loading efficiency and lower aggregation. The loading efficiency of CPT could be more than 96% and a steady release rate of CPT was kept for twenty six days. Moreover, the mPEG- b-PVL polymeric micelles offered good protection of CPT lactone form at 37 °C for sixteen days. The copolymers showed no cytotoxicity towards L929 mouse muscular cells when incubated for one day. Taken together, the mPEG- b-PVL copolymer has potential to be used for the delivery of CPT or other similar drugs.

Macromolecular synthesis using mesoporous zeolites

Mesoporous zeolites such as MCM-41 were found to serve as nano-flasks for free radical polymerization of methyl methacrylate (MMA), where the formation of long-lived propagating radicals was observed. Al-MCM-41 with a Lewis-acidic aluminosilicate framework catalyzed living ring-opening polymerization of cyclic esters such as δ-valerolactone and ϵ-caprolactone, to give narrow molecular-weight-distribution polyesters. With Ti-MCM-41, a titanate-containing mesoporous silica, ring-opening polymerization of δ-valerolactone also took place to give a high molecular-weight polyester. On the other hand, with Ti-MCM-41 in the presence of methylaluminoxane (MAO), ethylene was polymerized to give a high molecular-weight, linear polyethylene.

Lewis Acid-Driven Accelerated Living Polymerization of Lactones Initiated with Aluminum Porphyrins. Chemoselective Activation of Ester Groups by Lewis Acid

Ring-opening polymerization of δ-valerolactone (δ-VL) initiated with (5,10,15,20-tetraphenylporphinato)aluminum methoxide ((TPP)AlOMe, 1; X = OMe) was dramatically accelerated upon addition of methylaluminum bis(2,6-di-tert-butyl-4-methylphenolate) (2a) and bis(2,4,6-tri-tert-butylphenolate) (2b) via coordinative activation of monomer, but was accompanied by transesterification, resulting in broadening of the polymer molecular weight distribution (MWD) at the later stage of polymerization. On the contrary, when methylaluminum bis(2,6-di-X-phenolate)s (X = Cl (2c), Br (2d), I (2e), and Ph (2f)) were used as Lewis acids, the polymerization proceeded also rapidly, retaining the narrow MWD. 13C NMR studies on the Lewis acid (2b or 2f)−δ-VL and −poly(δ-VL) mixtures showed that the coordination abilities of 2b and 2f toward the monomer ester group are comparable to each other, while 2f shows a lower affinity to the polymer ester group than 2b. 2a was also able to accelerate the polymerization of β-butyrolactone (β-BL) with (TPP)AlOMe or (5,10,15,20-tetraphenylporphinato)aluminum chloride ((TPP)AlCl, 1; X = Cl) to different extents depending on the mode of ring scission, where the MWD of the polymer remained narrow throughout the accelerated polymerization (Mw/Mn = 1.1−1.2).

Cationic grafting from carbon black. III. Grafting of polyesters from carbon black by ring-opening polymerization of lactones initiated by COClO4 groups on carbon black

It was found that the cationic ring-opening polymerization of δ-valerolactone (VL), e-caprolactone (CL), and β-propiolactone (PL) was initiated by carbon black containing CO+ClO groups, which were introduced by the reaction of COCl groups with AgClO4. The polyester was propagated from CO+ClO groups and effectively grafted onto carbon black surface. The polymerizability of these lactones by CO+ClO groups decreased in the following order: VL > CL > PL. The increasing temperature of the polymerization caused an increase in the rate of the chain transfer reaction of the growing chains and brought about the decrease of grafting ratio of polyester onto carbon black.