Polymerization Of CL Research Articles

Poly(ε-caprolactone)-grafted-chitosan copolymers: Synthesis and use as tunable and biodegradable coating for water soluble fertilizers

The urgent need for efficient agriculture to increase crop and food has fueled the development of coated fertilizers with a slow-release kinetics, water economy and full degradability to avoid negative environmental impact. In this context, we herein report the synthesis of poly(ε-caprolactone) (PCL) grafted from chitosan (CS) as a new class of biodegradable coating materials. The CS-g-PCL were prepared following a one-pot, two-step strategy, in which the primary amines of CS first react with ε-caprolactone (CL) to form CL-oligomers linked to CS via amide bonds terminated with hydroxyls, which together with the native hydroxyls of CS initiate the ring-opening polymerization of CL after addition of Sn(C ≡ CPh)4 as catalyst. Owing to the great stability of the used catalyst, the high molar mass of PCL grafted onto CS was successfully obtained under trivial open-air conditions. Different copolymers (CS-g-PCL) were prepared by varying the CS content. The structural characterization of CS-g-PCL was carried out using FTIR, 1H NMR, X-ray diffraction, contact angle and size exclusion chromatography (SEC) while the thermal and mechanical characterization of the prepared CS-g-PCL were compared to the neat PCL. Next, using a laboratory rotary drum, CS-g-PCL was implemented to uniformly coat granular diammonium phosphate fertilizer (DAP). Consequently, the kinetic releases of nitrogen and phosphorus were significantly delayed compared to that observed from uncoated DAP (conventional fertilizers). Finally, the degradation of CS-g-PCL was examined under aerobic conditions and showed a significant increase in their biodegradability with respect to neat PCL.

Poly(Ether-Ester)-Based Solid Polymer Electrolytes with High Li-Ion Transference Number for High Voltage All-Solid-State Lithium Metal Batteries

Considering the lower room temperature ionic conductivity, Li-ion transference number, and narrow electrochemical stability window in all-solid-state polymer electrolytes (ASSPEs)-based lithium metal batteries (LMBs), it is of particular necessity to find plausible strategies to accomplish these issues. In this paper, poly(ε-caprolactone-co-1,5-dioxepan-2-one) (PDCL)-based poly(ether-ester) ASSPEs have been successfully fabricated by the random ring-opening polymerization of cyclic CL and DXO. The PDCL-SPE exhibits a high ion conductivity of 3.54 × 10–5 S cm–1 at 30 °C with a high Li-ion transference number (0.62) and a superior electrochemical stability (5.1 V). FT-IR spectra confirm the synergistic effect of ether and carbonyl of ester from the main chain of PDCL, which is superior to the dissociation of lithium salts and facilitation the motivation of lithium ions. Furthermore, the assembled LiFePO4/PDCL-SPE/Li batteries displayed low interfacial resistance, Li dendrite suppression, high specific capacity, and excellent cyclic performance (capacity retention of 85% after 200 cycles at 0.1 C). The high-voltage LiNi0.5Co0.2Mn0.3O2/PDCL-SPE/Li batteries also exhibits good cycling performance and durability.

Ring-opening polymerization of ε-caprolactone and L-lactide using ethyl salicylate-bearing zinc complexes as catalysts

A series of zinc complexes bearing ethyl salicylates were synthesized, and their catalytic activity in the polymerization of ε-caprolactone (CL) and l-lactide (LA) was investigated. In CL polymerization, the catalytic activity of Zn complexes was promoted by ligands with the substituents at the ortho position of phenolates, such as the 2-methyl group of L6MeZnEt (40 min, 94% conversion at 25 °C, [CL] = 2.0 M) and the 2,4-di‑tert‑butyl groups of LBuZnEt (55 min, 93% conversion at 25 °C, [CL] = 2.0 M). In LA polymerization, the catalytic activity was promoted by ligands with electron-donating substituents, such as the 4-methyl group of L4MeZnEt (55 min, 90% conversion at 50 °C, [LA] = 0.5 M) and the 2,4-di‑tert‑butyl group of LBuZnEt (60 min, 90% conversion at 50 °C, [LA] = 0.5 M). Density functional theory calculations revealed that the polymerization requires the detachment of a bridging alkoxide group from one Zn center to form an intermediate II-CL; bulky ligands may facilitate this unfavored dissociation process (from I-CL to II-CL). In LA polymerization, ligands with electron-withdrawing groups increase the Lewis acidity of Zn centers; the detachment of coordination atoms from the Zn atom is difficult; hence, the carbonyl group of ring-opening LA back binds to the Zn center to form a low-energy intermediate trip and then hinders another LA coordination.

A Topology‐Defined Polyester Elastomer from CO2 and 1,3‐Butadiene: A One‐Pot‐One‐Step “Scrambling Polymerizations” Strategy

AbstractIt is significant and challenging to use CO2 to produce polymeric materials, especially with olefins. Here, a novel strategy named “scrambling polymerizations” is designed and performed for the copolymerization of a CO2‐and‐1,3‐butadiene‐derived valerolactone, 3‐ethylidene‐6‐vinyltetrahydro‐2H‐pyran‐2‐one (EVL), with ϵ‐caprolactone (CL) to prepare polyesters. Anionic ring‐opening polymerization of CL and conjugated addition oligomerization of EVL take place individually to form PCL and EVL oligomers, respectively. Then EVL oligomers insert into PCL by transesterification resulting in polyester P(CL‐co‐EVL) with a tunable topology and composition. The non‐cytotoxic and degradable polyester network with elongation at break of >600 % can be used as an elastomer. We propose a method to provide polyester elastomers from CO2 and olefins for the first time, and expand the potential of transformation from sustainable feedstocks to polymeric materials.

A Topology-Defined Polyester Elastomer from CO2 and 1,3-Butadiene: A One-Pot-One-Step "Scrambling Polymerizations" Strategy.

It is significant and challenging to use CO2 to produce polymeric materials, especially with olefins. Here, a novel strategy named "scrambling polymerizations" is designed and performed for the copolymerization of a CO2 -and-1,3-butadiene-derived valerolactone, 3-ethylidene-6-vinyltetrahydro-2H-pyran-2-one (EVL), with ϵ-caprolactone (CL) to prepare polyesters. Anionic ring-opening polymerization of CL and conjugated addition oligomerization of EVL take place individually to form PCL and EVL oligomers, respectively. Then EVL oligomers insert into PCL by transesterification resulting in polyester P(CL-co-EVL) with a tunable topology and composition. The non-cytotoxic and degradable polyester network with elongation at break of >600 % can be used as an elastomer. We propose a method to provide polyester elastomers from CO2 and olefins for the first time, and expand the potential of transformation from sustainable feedstocks to polymeric materials.

One‐pot sequence‐selective synthesis of polylactone‐containing block terpolymers based on renewable terpenoid‐derived monomer and a simple organocatalyst

AbstractIn this work, we report the synthesis and polymerization performances of terpenoid‐derived camphoric anhydride (CA). Utilizing simple organo‐base tBuP2 as the catalyst, CA can polymerize with various epoxides by efficient and controlled ring‐opening alternating copolymerization (ROAC) to afford perfectly alternating poly(CA‐alt‐epoxide). Kinetic study shows that the polymerization proceeds following zero‐order dependence on the concentration of CA. The self‐switchable terpolymerization from the mixture of CA, propylene oxide (PO) and ε‐caprolactone (CL) is conducted under the catalysis of tBuP2. First, ROAC of CA and PO is carried out exclusively with benzyl alcohol as initiator. Then, block copolymer (BCP) poly(CA‐alt‐PO)‐b‐PCL is obtained via the sequential polymerizations after the complete consumption of CA. The followed ring‐opening polymerization (ROP) of CL is initiated by the terminal hydroxyl of the ROAC‐resulted poly(CA‐alt‐PO) polyester without external stimulus. During the process, the excess PO compound remains intact. The one‐pot synthesis displays distinct living nature and perfect chemoselectivity. The as‐prepared terpenoid‐derived alternating and BCP's exhibit elevated thermal properties.

Expanding the Scope of Boron-Based Ate Complexes by Manipulating Their Reactivity: The Case of Cyclic Esters and Their (Co)Polymers

The value and merit of triethylborane (TEB)-based ate complexes for the synthesis of various oxygenated polymers have been recently illustrated through successful examples of homopolymerization of epoxides and of their copolymerization with CO2, CS2, COS, anhydrides, isocyanates, etc. To further expand the scope of TEB-based initiating systems to a broader family of oxygenated polymers, they were used in this study to anionically polymerize cyclic esters and to copolymerize the latter monomers with propylene oxide (PO). To promote a fast and controlled ring-opening polymerization (ROP) of cyclic esters, hydrogen-bonding donors such as amines and (thio)ureas were added to TEB-based ate complexes used as initiators. Only under these conditions could the ROP of ε-caprolactone (CL), δ-valerolactone (VL), and l-lactide (LLA) proceed under controlled conditions with hardly detectable intra- or intermolecular transesterifications. The role of amines and (thio)ureas when used alone or together in association with these boron-based initiators is discussed in detail. The controlled character of the polymerization of CL, VL, and LLA is attested by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-ToF MS) and other characterization techniques. As examples of the far-reaching potential of these borane-based ate complexes, random P(PO-co-VL) copolymers were derived by statistical copolymerization of VL with PO and various well-defined block copolymers─PPO-b-PVL, PVL-b-PPO, PPO-b-PCL, PPO-b-PLLA, and PPO-b-PVL-b-PPO─were grown by sequential polymerization of the corresponding monomers.

Ring-Opening Polymerization of ε-Caprolactone by Using Aluminum Complexes Bearing Aryl Thioether Phenolates: Labile Thioether Chelation.

In this study, aluminum complexes bearing ferrocene-based and arylthiomethylphenolate ligands were synthesized, and their catalytic activity for ε-caprolactone (CL) polymerization was investigated. The catalytic activity of the reduced form of Al complexes was higher than that of the oxidized form. The CL polymerization rate of the reduced form fcO2AlMe (75 min, conversion = 100%) was higher than that of the oxidized form fcoxO2AlMe (4320 min, conversion = 45%), and the CL polymerization rate of fc(OAlMe2)2 (40 min, conversion = 100%) was higher than that of fcox(OAlMe2)2 (60 min, conversion = 97%). Electron deficiency substituents on phenolate decreased the catalytic activity of Al complexes bearing arylthiomethylphenolate ligands. Density functional theory calculations revealed that thioether coordination stabilized the transition state (TS1) and that the oxidized form fcox(OAlMe2)2 exhibited weaker thioether coordination and higher activation energy in TS1 compared with those of the reduced form fcO2AlMe. In addition, our study determined that the thioether group is a suitable chelating group for Al catalysts in CL polymerization due to its labile nature.

Titanium ONN-(phenolate) Alkoxide Complexes: Unique Reaction Kinetics for Ring-Opening Polymerization of Cyclic Esters.

The synthesis, characterization, and polymerization kinetics of four new titanium ONN-(phenolate) alkoxide catalysts were studied. Each catalyst is fluxional at room temperature, suggesting the ligand amine arm may be labile, but adopts a fac geometry in solution at low temperature (223 K) and in the solid state. All catalysts are active for the ring-opening polymerization of both ε-caprolactone (CL) and rac-lactide (LA). GPC analysis indicates that the well-known coordination-insertion mechanism is being followed. However, whereas the typical first-order dependence on monomer concentration is observed in CL, an unexpected zeroth-order dependence is observed with LA. This suggests that, in the case of LA, catalyst saturation occurs and a Michaelis-Menten model can be used to explain the kinetics. An initial mechanism is discussed within this model that proposes CL polymerization proceeds by a 7-coordinate intermediate, whereas LA polymerization adopts a 6-coordinate intermediate, facilitated by the ligand amine arm. Attempts to isolate catalyst-monomer intermediates are ongoing.

Collaboration between Trinuclear Aluminum Complexes Bearing Bipyrazoles in the Ring-Opening Polymerization of ε-Caprolactone.

Trinuclear aluminum complexes bearing bipyrazoles were synthesized, and their catalytic activity for ε-caprolactone (CL) polymerization was investigated. DBu2Al3Me5 exhibited higher catalytic activity than did the dinuclear aluminum complex LBu2Al2Me4 (16 times as high for CL polymerization; [CL]:[DBu2Al3Me5]:[BnOH] = 100:0.5:5, [DBu2Al3Me5] = 10 mM, conversion 93% after 18 min at room temperature). Density functional theory calculations revealed a polymerization mechanism in which CL first approached the central Al atom and then moved to an external Al. The coordinated CL ring was opened because the repulsion of two tert-butyl groups on the ligands pushed an alkoxide initiator on an external Al to initiate CL. In these trinuclear Al catalysts, the central Al plays a role in monomer capture and then collaborates with the external Al to activate CL, accelerating polymerization.

New way of anionic ring-opening copolymerization of \u03b2-butyrolactone and \u03b5-caprolactone: determination of the reaction course

Poly(ε-caprolactone)-block-poly(β-butyrolactone) copolymers were prepared in two-step synthesis. Firstly, poly(ε-caprolactone) (PCL) was obtained by anionic ring-opening polymerization of CL initiated with anhydrous KOH activated 12-crown-4 cation complexing agent. Reaction was carried out in tetrahydrofuran solution and argon atmosphere at room temperature. Then, β-butyrolactone (BL) and 18-crown-6 were added to the system, resulting in PCL-block-PBL copolymer, which contains after methylation hydroxyl starting group and methyl ester end group. The main product was contaminated with PCL and PBL homopolymers formed in a side reactions. 13C NMR technique was used for determination of chemical structure of polymers obtained. The course of the studied processes was proposed. MALDI-TOF technique was used to reveal the macromolecules’ architecture where several series were found. The identified series shown that mainly copolymeric macromolecules were formed with scare contribution of homopolymeric polybutyrolactone with trans-crotonate starting groups and polycaprolactone, which is congruent with the proposed reaction mechanism. Moreover, critical approach concerning previously reported PCL-block-PBL copolymer synthesis by use of NaH as initiator was also presented.

N-heterocyclic ligand optimization for aluminum complexes in ε-caprolactone and L-Lactide polymerization

A series of aluminum complexes bearing heterocyclic amine ligands were synthesized, and their application in ε-caprolactone (CL) and L-Lactide (LA) polymerization and copolymerization were studied. The CL polymerization results revealed that ligands containing the higher electronegativity atom increased the polymerization rate of CL polymerization. Among these Al complexes, NON-AlMe3 bearing benzofurazan ligand was the best catalyst in CL polymerization ([NON-AlMe3] = 10 mM, conversion = 94% after 4 min at room temperature). In LA polymerization, the catalytic trend of Al complexes was random, and NCN-AlMe3 bearing 1-benzylbenzimidazole ligand was the best catalyst ([NCN-AlMe3] = 10 mM, conversion = 90% after 45 min at 80 °C). The selectivity of the production of a PLA-gradual-PCL copolymer could be controlled by different Al complexes. Our study revealed that the four-coordinated trimethyl Al complexes bearing heterocyclic amine ligands were easily synthesized and constitute an ideal catalyst design in CL polymerization.

Recent Advances in the Synthesis and Analysis of Polyamide 6 and Products Therefrom: From Polymerization Chemistry of ε-Caprolactam to Thermoplastic Resin Transfer Molding (T-RTM)

Significant research and developments are taking place in the field of synthetic polyamides (Nylons). One of the most investigated members of this family of polymers is poly (ε-caprolactam) (PCL, Polyamide 6, PA6, Nylon 6). Herein, a brief overview will be presented on the major recent advancements in the anionic ringopening polymerization (AROP) of ε-caprolactam (CL) by the initiating combinations of metal lactamates and carbamoylcaprolactams and by some other initiating systems, e.g. protected N-heterocyclic carbenes , NaHMDI and σ-borane-barium complexes. The in situ polymerization of CL in the presence of additives, such as flame retardants, reinforcing agents and fillers, is also discussed. Examples are presented on the determination of the molecular weight distributions (MWD) and average molecular weights of Polyamide 6 by GPC (SEC) measurements with 1,1,1-trifluoroethanol as eluent used routinely in our laboratories. Finally, a glimpse will be provided into the ongoing intensive research related to thermoplastic resin transfer molding (T-RTM) processes aiming at producing Polyamide 6 products, such as reinforced PA6 and composites, by rapid in situ polymerization of CL.

Enhanced Tensile Properties of Multi-Walled Carbon Nanotubes Filled Polyamide 6 Composites Based on Interface Modification and Reactive Extrusion.

To induce uniform dispersion and excellent interfacial properties, we adopted a strategy of combining both polyamide 6 (PA6) grafting for multi-walled carbon nanotubes (MWCNTs) and reactive extrusion of PA6 matrix, based on anionic ring-opening polymerization of ε-caprolactam (CL). Compared to –COOH and –NCO treatments of MWCNTs, enhanced MWCNT dispersion and tensile properties of the composites were achieved using the applied strategy, and the tensile strength and modulus of the PA6-grafted MWCNT-filled PA6 composites were 5.3% and 20.5% higher than those of the purified MWCNT-filled PA6 composites, respectively. In addition, they were almost similar to the theoretical ones calculated by the modified Mori–Tanaka method (MTM) assuming a perfect interface, indicating that the tensile properties of MWCNT-filled PA6 composites can be optimized by PA6 grafting and reactive extrusion based on the anionic ring-opening polymerization of CL due to uniform MWCNT dispersion and excellent interfacial property.

Tuning the thermal properties of poly(ethylene)‐like poly(esters) by copolymerization of ε‐caprolactone with macrolactones, in the presence of a pyridylamidozinc(II) complex

ABSTRACTLinear aliphatic poly(ester)s, as thermoplastic materials, are more and more envisaged as the potential “green” alternative to traditional plastics. Aliphatic polyesters having long methylene chain behave as “polyethylene‐like” materials and can be prepared by ring‐opening polymerization (ROP) of macrolactones. A pyridylamidozinc(II) complex was used for the ROP of ε‐caprolactone (CL) and of two large ring size lactones, the ω‐6‐hexadecenlactone (6HDL) and the ω‐pentadecalactone (PDL). High turnover frequencies were observed for the CL polymerization, while for the macrolactones, an entropy‐driven behavior was recognized. Random copolymerizations of the PDL with 6HDL and of the macrolactones with CL were successfully achieved, and the copolymer microstructure was ascertained by NMR and MALDI analyses. The copolymer melting temperatures, measured by DSC, and the thermal degradation behavior, studied by TGA in nitrogen and air atmosphere, were dependent on the copolymer's composition. © 2020 Wiley Periodicals, Inc. J. Polym. Sci.2020,58, 528–539

Polycaprolactone/Graphene Nanocomposites: Synthesis, Characterization and Mechanical Properties of Electrospun Nanofibers

In this study, three polymer nanocomposites based on poly(e-caprolactone) (PCL) grafted on the graphene quantum dot (GQD), hydroxypropyl cellulose (HPC)/GQD (GQD: HPC = 1:1; w/w) and graphene oxide (GO) with 1.6 wt% of e-caprolactone (CL) were synthesized via in situ ring opening polymerization of CL. The synthesized nanocomposites were characterized using FTIR, 1H NMR, and contact angle measurements. The lowest molecular weight for PCL/GO was obtained according to 1H NMR spectra. Crystalline structure and thermal behavior of composites were investigated by XRD, DSC and TGA. The results showed that the presence of HPC and graphene-based nanofillers in nanocomposite can affect the hydrogen bonding interaction with PCL chains, melting temperature (Tm), degree of crystallinity [Xc(%)] and the size of crystals. According to the results, PCL/GQD-HPC had higher Tm, lower Xc(%), longer PCL moieties and smaller crystals. Also, the TGA results indicated that the nanocomposites were thermally more stable than the pure PCL. Moreover, a conventional electrospinning process was used to prepare nanofibers of synthesized nanocomposites blended with PCL (50:50; w/w). SEM images and mechanical behavior study of obtained nanofibers depicted that the PCL/(PCL/GQD-HPC) nanofibers have a significant increment in the average diameter, tensile modulus and strength in comparison with other composites.

Improvement in zinc complexes bearing Schiff base in ring-opening polymerization of ε-caprolactone: A five-membered ring system

The ring-opening polymerizations of ε-caprolactone (CL) using 5- and 6-membered ring Zn complexes bearing Schiff base as catalysts were comparatively studied. The 5-membered ring Zn complexes exhibited a considerably higher polymerization rate than the 6-membered ring Zn complexes (2–12 fold for CL polymerization) did. X-ray data revealed that 5-membered ring L5-Ph2Zn creates larger empty space around the Zn center than 6-membered ring L6-Bn2Zn. This allows higher interaction between the initiator and Zn complex and easy CL coordination.

Polymerization of ε-caprolactone with degraded PET for its functionalization

Poly(caprolactone) (PCL) was synthesized from the polymerization of e-caprolactone (CL) with degraded poly(ethylene terephthalate) (PET) for its functionalization using heptamolybdate of ammonium and tin(II) 2-ethylhexanoate, as catalyst and initiator, respectively. Polymerization of CL with bis(2-hydroxyethyl) terephthalate (BHET) was carried out to make a comparison. From the analysis by FTIR, the functional groups of polycaprolactone and degraded PET were identified by FTIR. The chemical shift at 165.59 ppm obtained by NMR corresponded to the chemical bond between the carbonyl of the PCL bound to the -CH2CO2-C10H8O4 of the degraded PET. The number average molar mass of polymer obtained was determined and its chemical structure was proposed. Crystallinity and the temperatures of melting and degradation depended of the mass of degraded PET used in the synthesis. Based on the proposed chemical structure, the synthesized polymer could be used in the preparation of other polymers.

Facile and cost-effective strategy for fabrication of polyamide 6 wrapped multi-walled carbon nanotube via anionic melt polymerization of ε-caprolactam

There is a growing demand for the development of a melt process-based nanocomposite manufacturing process capable of minimizing the incorporation of expensive carbon nanotubes (CNTs) by inducing a uniform dispersion of multi-walled CNTs (MWNTs). In this study, we proposed a nanocomposite manufacturing process that includes both physical particle mixing using high-speed rotation and anionic polymerization of ε-caprolactam (CL) to induce a uniform dispersion of MWNTs. MWNTs were uniformly dispersed by powder mixing and then wrapped with polyamide 6 polymers by in-situ polymerization of CL. The synergistic effect of the two sub-processes resulted in an enhanced dispersion of MWNTs and prevented aggregation of the MWNTs. The composites fabricated by the proposed process exhibited electrical conductivities of 4.49 × 10−5 S/m and 1.45 × 10 S/m at 1 wt% and 3 wt% MWNTs, respectively, indicating that by applying the proposed process it is possible to incorporate a smaller amount of MWNT to achieve electrical conductivities applicable for electrostatic discharge (ESD) (>1 X 10−5 S/m) and electromagnetic interference shielding effectiveness (EMI SE) (>10 S/m) applications. An ESD chip tray and EMI SE mobile phone case were fabricated using the prepared composite, and it was verified that the ESD and EMI SE performances can be realized.

Effect of process variations of polycaprolactone modification on wood durability, dimensional stability and boron leaching

Abstract In this study, in situ graft polymerization of ε-caprolactone (CL) was studied for its potential to limit boric acid (BA) leaching from wood, and to increase the dimensional stability and biological durability of wood against Coniophora puteana and Trametes versicolor fungi. For this purpose, CL monomer with/without BA was impregnated into wood, and the monomer was polymerized in wood cell walls using various methods and combinations of reactants. It was found that biodegradable polycaprolactone (PCL) grafting at high monomer concentrations could inhibit fungal degradation of wood cell walls, as well as improve the dimensional stability of wood up to 55% and reduce water uptake (WU) by about 50%. However, inductively coupled plasma-optical emission spectrometry (ICP-OES) analysis revealed that in situ graft polymerization of CL is not an effective method to prevent BA leaching from wood.