Cationic ring‐opening polymerization of ϵ‐thionocaprolactone: Selective formation of polythioester

Cationic ring‐opening polymerization of ϵ‐thionocaprolactone was examined. The corresponding polythioester with the number‐average molecular weight (M_n ) of 57,000 was obtained in the polymerization with 1 mol % of BF₃ · OEt₂ as an initiator in CH₂Cl₂ at 28 °C for 5 h with quantitative monomer conversion. The M_n of the polymer increased with the solvent polarity and monomer‐to‐initiator ratio. No polymerization took place below −30 °C, and the monomer conversion and M_n of the polymer increased with the temperature in the range of −15 to 28 °C. The increase of initial monomer concentration was effective to improve the monomer conversion and the M_n of the obtained polymer. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4057–4061, 2000     

Controlled synthesis and fluorescent properties of poly(9-(4-vinylbenzyl)-9H-carbazole) via nitroxide-mediated living free-radical polymerization

The functional polymer containing carbazole unit, [(poly(9-(4-vinylbenzyl)-9H-carbazole) (PVBK)], was successfully prepared via nitroxide-mediated living free-radical polymerization of 9-(4-vinylbenzyl)-9H-carbazole (VBK). The controlled features of the polymerization were confirmed by the linear increase in the molecular weight with the monomer conversion while keeping the relative narrow molecular weight distribution (M_w/M_n ? 1.51), and successful chain extension with styrene. The resulting polymer absorbed light in the 305-355 nm range and exhibited fluorescent emission at 350 nm. The fluorescent intensity of the polymer was lower than that of monomer and was affected by the properties of the different solvents, which decreased in the following order: DMF > THF > CHCl₃ at the same concentration of carbazole units. The fluorescence intensity of the polymer was apparently influenced by chromophore concentration, and the maximum value was obtained when the carbazole unit concentration was around 8 × 10⁻⁵ mol/L. Moreover, it was shown that the strong fluorescence of PVBK can be quenched by methyl acrylate (MA).     

Ring-Opening polymerization of ε-caprolactone by rare earth coordination catalysts. I. Characteristics,kinetics, and mechanism of ε-caprolactone polymerization with nd(acac)3.3H2O-ALET3 system

Ring-opening polymerization of ε-caprolactone has been carried out by using rare earth coordination catalysts for the first time. The rare earth compounds, RE(acac)₃.3H₂O, Nd(P₂₀₄)₃, Nd(P₅₀₇)₃, Nd(naph)₃, Nd(BA)₃.2H₂O, etc. (where RE = La, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Lu, Y; acac = acetylacetone; BA = benzoylacetone), combined with trialkyl aluminum, greatly increased the degree of conversion and the molecular weight of poly(ε-caprolactone) (PCL). The influence of reaction conditions on the polymerization of ε-caprolactone catalyzed by the Nd (acac)₃.3H₂O-AlEt₃ system has been examined in detail. The kinetics indicates that the polymerization rate has the first-order in monomer and a half-order in catalyst. The overall activation energy of the ring-opening polymerization amounts to 59.4 kJ/mol. By IR and UV-Vis spectra, ¹H- and ¹³C-NMR data, it is assumed that the ring-opening polymerization of ε-caprolactone catalyzed by the Nd(acac)₃.3H₂O-AlEt₃ system proceeds via complexation of monomer to catalyst, acyl-oxygen cleavage insertion propagation mechanism. © 1994 John Wiley & Sons, Inc.     

Cationic polymerization of γ-methyl- and α-methylphenylallene

The cationic polymerizations of γ-methylphenylallene ( 1 ) and α-methylphenylallene ( 2 ) were carried out with some Lewis acids at 25 and 0°C in dichloromethane to obtain the corresponding polymers through allyl cations, respectively. Tin (IV) chloride was found to be an effective catalyst for the cationic polymerization of both allenes 1 and 2 compared with other Lewis acids. Thus, in the polymerization of 1 , methanol-insoluble polymer was only obtained using Tin (IV) chloride, and M?_n of methanol-insoluble polymer obtained by Tin (IV) chloride was the highest in the polymerization of 2 . From the analysis of ¹H- and ¹³C-NMR spectra of the obtained polymers, the polymer from 1 consisted of two kinds of units polymerized by each double bonds of allene 1 , whereas the polymer from 2 consisted of only one unit polymerized by terminal double bond of allene 2 . Moreover, effect of solvent on the cationic polymerizations of 1 and 2 were discussed.     

Grafting of poly(ε‐caprolactone) onto maghemite nanoparticles

We report the coating of maghemite (γ‐Fe₂O₃) nanoparticles with poly(ε‐caprolactone) (PCL) through a covalent grafting to technique. ω‐Hydroxy‐PCL was first synthesized by the ring‐opening polymerization of ε‐caprolactone with aluminum isopropoxide and benzyl alcohol as a catalytic system. The hydroxy end groups of PCL were then derivatized with 3‐isocyanatopropyltriethoxysilane in the presence of tetraoctyltin. The triethoxysilane‐functionalized PCL macromolecules were finally allowed to react on the surface of maghemite nanoparticles. The composite nanoparticles were characterized by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). Effects of the polymer molar mass and concentration on the amount of polymer grafted to the surface were investigated. Typical grafting densities up to 3 μmol of polymer chains per m² of maghemite surface were obtained with this grafting to technique. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 6011–6020, 2004     

On the behavior of organophosphorus lactam derivatives during anionic polymerization of ε-caprolactam

This article deals with the anionic polymerization of ε-caprolactam in the presence of N-substituted phosphorus-containing derivatives of ε-caprolactam: diethyl-(N-caprolactam)-phosphonite (PL₁); diethyl-(N-caprolactam)-phosphonate (PL₂), and 2,5-dichlorophenyl-bis-(N-caprolactam)-phosphinate (PL₃). It has been found out that PL₁ and PL₃ had an accelerating effect on the anionic polymerization of ε-caprolactam. The polymerization runs at high velocity and high degree of conversion. PL₂ does not accelerate the anionic polymerization of ε-caprolactam, but when the polymerization is activated by a strong activator of acyl lactam type, and the PL₂ concentration is commensurate with that of the activator, the process runs at a slightly lower rate and at a relatively high degree of conversion. The kinetics of the anionic polymerization in the presence of the three compounds was investigated. Equations describing the effect of the reagents on the polymerization rate were suggested. The activating energy of the polymerization was found out. The different actions of PL₁, PL₂, and PL₃ during the anionic polymerization of ε-caprolactam were explained by their structural differences.     

Monoaryloxo ytterbium(III) chlorides supported by β‐diketiminato ligands as novel initiators for the living ring‐opening polymerization of ε‐caprolactone

Ring‐opening polymerization of ε‐caprolactone (ε‐CL) was carried out using β‐diketiminato‐supported monoaryloxo ytterbium chlorides L¹Yb(OAr)Cl(THF) (1) [L¹ = N,N′‐bis(2,6‐dimethylphenyl)‐2,4‐pentanediiminato, OAr = 2,6‐di‐tert‐butylphenoxo‐], and L²Yb(OAr′)Cl(THF) (2) [L² = N,N′‐bis(2,6‐diisopropylphenyl)‐2,4‐pentanediiminato, OAr′ = 2,6‐di‐tert‐butyl‐4‐methylphenoxo‐], respectively, as single‐component initiator. The influence of reaction conditions, such as polymerization temperature, polymerization time, initiator, and initiator concentration, on the monomer conversion, molecular weight, and molecular weight distribution of the resulting polymers was investigated. Complex 1 was well characterized and its crystal structure was determined. Some features and kinetic behaviors of the CL polymerization initiated by these two complexes were studied. The polymerization rate is first order with respect to monomer. The M_n of the polymer increases linearly with the increase of the polymer yield, while polydispersity remained narrow and unchanged throughout the polymerization in a broad range of temperatures from 0 to 50 °C. The results indicated that the present system has a “living character”. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1147–1152, 2006     

Homo‐ and random copolymerizations of ω‐pentadecalactone with ε‐caprolactone using isothiourea‐based dual catalysis

In this study, the catalytic behavior of dual catalysis based on isothioureas (ITUs) for ring‐opening polymerization (ROP) of macrolactone ω‐pentadecalactone (PDL) and its copolymerization with ε‐caprolactone (CL) has been investigated in detail. In the presence of benzyl alcohol (BnOH) initiator, 2,3,6,7‐tetrahydro‐5H‐thiazolo[3,2‐a]pyrimidine (THTP) acted as a representative organic compound, which coupled with magnesium halides (MgX₂) as cocatalysts and catalyzed the polymerization in toluene at 70 °C. Under suitable conditions, an array of polymers with controlled molecular weights and relatively narrow molecular weight distributions were synthesized. The formation of homopolymers and copolymers with different architectures was verified using GPC, DSC, NMR, and matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐ToF) mass. The MALDI‐ToF mass spectrometry (MS) analysis of poly(ω‐pentade‐calactone) (PPDL) provided direct evidence for the successful initiation of ROP of PDL using BnOH to obtain linear PPDL with a very small amount of oligomer. The NMR analysis indicated that the arrangements of PDL and CL units in the copolymer chains were completely random. The thermal stability of copolymers was composition dependent and increased with the increase in the content of PDL unit. Furthermore, the proposed polymerization mechanism is a dual catalytic mechanism. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019     

3α,7α,12α-三甲基丙烯酰基胆酸甲酯的制备与聚合物特性研究

以甲基丙烯酰氯为酰化试剂，合成了3α，7α，12α-甲基丙烯酰胆酸甲酯(CAME3MA)，研究了CAME3MA的光引发本体聚合和溶液聚合反应，并且对CAME3MA及其聚合物的特性进行了表征．实验表明：CAME3MA的本体光引发聚合转化率随光照时间的延长逐渐增加并达到一个最大值，最终的聚合转化率在36％左右，溶液聚合得到线性聚合物。     

稀土硫化物：e–己内酯开环聚合新催化剂

The ring-opening polymerization （ROP） of ε-caprolactone （ε-CL） using lanthanide thiolate complexes [（CH3CsH4）2Sm（μ-SPh）（THF）]2 （1） and Sm（SPh）3（HMPA）3 （2） as initiators has been investigated for the first time. Both of 1 and 2 were found to be highly efficient initiators for the ROP of ε-CL. The poly（ε-caprolactone） （PCL） with molecular weight Mn up to 1.97 ×10^5 and relatively narrow molecular weight distributions （1.20〈MW/Mn〈 2.00） have been obtained in high yield in the temperature range of 35-65℃. According to the polymer yield, 2 showed much higher activity than 1. However, the number-average molecular weight of PCL obtained with 2 was much lower than with 1. The possible polymerization mechanism of the ε-CL polymerization has been proposed based on the results of the end group analysis of the ε-CL oligomer.     

Initiating system Me_3SiCl/AlCl_3 for cationic polymerization of 1,3-pentadiene in toluene

Cationic polymerization of 1,3-pentadiene (PD) initiated by trimethylsilyl chloride/aluminium chloride (TMSCl/AlCl3) was carried out in toluene at 30℃.The polymer yield was increased by the addition of TMSC1.However,introduction of TMSC1 gave rise to a drop of the polymer molecular weight.Kinetic results demonstrated that the polymerization initiated by TMSCl/AlCl3 was 2.8 times faster than that induced by AlCl3 alone.Various ethers and ketones were used to mediate the initiating system TMSCl/AlCl3.The polymer yield and molecular weight of the polymer were decreased in the presence of ether.Ketones and ethers had different effects on the polymerization,and the polymer yield and molecular weight were lower than those initiated by AlCl3 alone or TMSCl/AlCl3 Structural evidence revealed that the polymerization was indeed initiated by AlCl3 and HCl rcsulting from hydrolysis of TMSC1 by adventitious water.     

The effect of AlR3 on propylene polymerization by rac‐(EBI)Zr(NMe2)2/AlR3/[CPh3][B(C6F5)4] catalyst

Ansa‐zirconocene diamide complex rac‐(EBI)Zr(NMe₂)₂ [rac‐1, EBI = ethylene‐1,2‐bis(1‐indenyl)] reacted with AlR₃ (R = Me, Et, iBu) or Al(iBu₂)H and then with [CPh₃][B(C₆F₅)₄] (2) in toluene in order to perform propylene polymerization by cationic alkylzirconium species, which are in situ generated during polymerization. Through the sequential NMR‐scale reactions of rac‐1 with AlR₃ or Al(iBu₂)H and then with 2, rac‐1 was demonstrated to be transformed to the active alkyzirconium cations via alkylated intermediates of rac‐1. The cationic species generated by using AlMe₃, AlEt₃, and Al(iBu₂)H as alkylating reagents tend to become heterodinuclear complex; however, those by using bulky Al(iBu)₃ become base‐free [rac‐(EBI)Zr(iBu)]⁺ cations. The activity of propylene polymerization by rac‐1/AlR₃/2 catalyst was deeply influenced by various parameters such as the amount and the type of AlR₃, metallocene concentration, [Al]/[2] ratio, and polymerization temperature. Generally the catalytic systems using bulky alkylaluminum like Al(iBu)₃ and Al(iBu)₂H show higher activity but lower stereoregularity than those using less bulky AlMe₃ and AlEt₃. The alkylating reagent Al(iBu)₃ is not a transfer agent as good as AlMe₃ or AlEt₃. The polymerization activities show maximum around [Al]/[2] ratio of 1.0 and increase monotonously with polymerization temperature. The overall activation energy of both rac‐1/Al(iBu)₃/2 and rac‐1/Al(iBu)₂H catalysts is 6.0 kcal/mol. As the polymerization temperature increases, the stereoregularity of the resulting polymer decreases markedly, which is demonstrated by the decrease of [mmmm] pentad value and by the increase of the amount of polymer soluble in low boiling solvent. The physical properties of polymers produced in this study were investigated by using ¹³C‐NMR, differential scanning calorimetry (DSC), viscometry, and gel permeation chromatography (GPC). © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1523–1539, 1999     

Radical polymerization and copolymerization of methyl α-(2-carbomethoxyethyl)acrylate,a dimer of methyl acrylate,as a polymerizable α-substituted acrylate

Polymerization and copolymerization of methyl α-(2-carbomethoxyethyl)acrylate (MMEA), which is known as a dimer of methyl acrylate, were studied in relation to steric hindrance-assisted polymerization. The propagating polymer radical from MMEA was detected as a five-line spectrum and quantified by ESR spectroscopy during the bulk polymerization at 40–80°C. The absolute rate constants of propagation and termination (κ_p and κ_t) for MMEA at 60°C (κ_p = 19 L/mol s and κ_t = 5.1 × 10⁵ L/mol s) were evaluated using the concentration of the propagating radical at the steady state. The balance of the propagation and termination rates allows polymer formation from MMEA. The polymerization rate of MMEA at 60°C was less than that of MMA by a factor of about 4 at a constant monomer concentration. Although no influence of ceiling temperature was observed at a temperature ranging from 40 to 70°C, addition-fragmentation in competition with propagation reduced the molecular weight of the polymer. The content of the unsaturated end group was estimated to be 0.1% at 60°C to the total amount of the monomer units consisting of the main chain. MMEA exhibited reactivities almost similar to those of MMA toward polymer radicals. It is concluded that MMEA is one of the polymerizable acrylates bearing a substituted alkyl group as an α-substituent. Characterization of poly(MMEA) was also carried out. © 1996 John Wiley & Sons, Inc.     

Darstellung und Kristallstruktur von Ca5Hg3 und Sr5Cd3

Preparation and Crystal Structure of Ca₅Hg₃ and Sr₅Cd₃ Both the incongruently melting compounds, Ca₅Hg₃ and Sr₅Cd₃, have been synthesized from stoichiometric amounts of the pure elements. They crystallize with the Cr₅B₃ type of structure: space group I4/mcm, Z = 4; Ca₅Hg₃ (Sr₅Cd₃): a = 818.9(1) (871.7(1)) pm, c = 1 470.1(3) (1 660.1(3)) pm, c/a = 1.80 (1.90), R = 2.33% (2.97%). The most remarkable fragments are dumbbells X₂, which have interatomic distances only slightly longer than the sum of Pauling's covalent radii: Hg? Hg (Cd? Cd) = 306 (298) pm. The structure can be constructed by rhombic dodecahedra as the only constituent moieties. These rhombic dodecahedra are built up by eight Ca (Sr) atoms and six Hg (Cd) atoms and are furthermore centered by an additional Ca (Sr) atom. Along [001] the rhombic dodecahedra share common vertices, but along [110] they are interconnected via common triangular faces. This kind of face sharing is responsible for the short distances obtained between the polyhedra, which leads to the occurrence of the dumbbells mentioned above.     

Hyperbranched polyimides prepared by ideal A2+B3 polymerization,non-ideal A2+B3 polymerization and AB2 self-polymerization

In this paper, hyperbranched polyimides having the same repeating unit were synthesized by employing ideal A₂+B₃ polymerization, non-ideal A₂+B₃ polymerization and AB₂ self-polymerization methods. The polymerization behavior, polymer properties were compared for three methods. Hyperbranched polyimides by ideal A₂+B₃ polymerization, non-ideal A₂+B₃ polymerization and AB₂ self-polymerization methods show apparent difference in many physical properties, such as inherent viscosity, glass transition temperature, and film formation behavior etc. The hyperbranched polymers by the non-ideal A₂+B₃ polymerization are suitable for smooth, flexible and self-standing film preparation, which provides useful information for hyperbranched polymers toward self-standing materials.     

Synthesis,characterization, electrochromic properties,and electrochromic device application of a novel star polymer consisting of thiophene end‐capped poly(ε‐caprolactone) arms emanating from a hexafunctional cyclotriphosphazene core

Hexa‐armed and thiophene (Thi) end‐capped poly(ε‐caprolactone) star polymer (N₃P₃‐(PCL‐Thi)₆), containing cyclotriphosphazene core, was prepared in a four‐step reaction sequence. Ring‐opening polymerization (ROP) and “click chemistry” techniques were employed in the first and final steps, respectively. Hexa‐armed PCL star polymer (N₃P₃‐(PCL‐OH)₆) was successfully synthesized via ROP of ε‐caprolactone (ε‐CL) by using hekzakis(p‐(hydroxymethyl)phenoxy) cyclotriphosphazene as the multisite initiator and tin(II) 2‐ethylhexanoate (Sn(Oct₂)) as the catalyst in bulk at 115 °C. Further modifications of the N₃P₃‐(PCL‐OH)₆ were accomplished by derivatization of the hydroxyl‐functional chain ends. The obtained N₃P₃‐(PCL‐OH)₆ was then reacted with 2‐bromo‐2‐methylpropanoyl bromide, and this led to a star polymer with bromide end groups, N₃P₃‐(PCL‐Br)₆. In the third step, N₃P₃‐(PCL‐Br)₆ was azidified with sodium azide (NaN₃) in DMF affording N₃P₃‐(PCL‐N₃)₆. Conversion of the azide chain end groups into Thi was quantitatively accomplished via the “click reaction” between N₃P₃‐(PCL‐N₃)₆ and prop‐2‐yn‐1‐yl 3‐thienyl acetate in the final step. Subsequently, the star polymer with six Thi chain ends (N₃P₃‐(PCL‐Thi)₆) was employed in electrochemical copolymerization with both pyrrole and Thi. Electrochromic properties and electrochromic device application of N₃P₃‐(PCL‐Thi)₆/PThi were also investigated. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3668–3682, 2010     

Poly(N-phenyl-2-hydroxytrimethylene amine): Its blends with poly(ϵ-caprolactone) and water-soluble polyethers

A new polymer with pendant hydroxyl groups, namely, poly(N-phenyl-2-hydroxytrime-thylene amine) (PHA), was synthesized by a direct condensation polymerization of aniline and epichlorohydrin in an alkaline medium. The new polymer is amorphous with a glass transition temperature (T_g) of 70°C. Blends of PHA with poly(ϵ-caprolactone) (PCL), as well as with two water-soluble polyethers, poly(ethylene oxide) (PEO) and poly(vinyl methyl ether) (PVME), were prepared by casting from a common solvent. It was found that all the three blends were miscible and showed a single, composition dependent glass transition temperature (T_g). FTIR studies revealed that PHA can form hydrogen bonds with PCL, PEO, and PVME, which are driving forces for the miscibility of the blends. © 1997 John Wiley & Sons, Inc.     

(CH3)3SiCl/TiCl4 INITIATING SYSTEM FOR CATIONIC POLYMERIZATION OF 1,3-PENTADIENE

Cationic polymerizations of 1,3-pentadiene (PD) initiated by trimethylsilyl chloride (TMSCl) incombination with TiCl_4 were carried out in n-hexane at 30℃. The yield of polymer was greatly increased bythe addition of TMSCl, indicating that the TMSCl/TiCl_4 combination is an efficient initiating system for PDcationic polymerization. However, the introduction of TMSCl gave rise to a drop in the molecular weight ofthe polymer. Kinetic results demonstrated that the polymerization initiated by TMSCl/TiCl_4 is 4.5 times fasterthan that induced by TiCl_4 alone. Various ethers were used to mediate the TMSCl/TiCl_4 initiating system.Adding diphenyl ether could increase both the yield and molecular weight of the polymer. Structural evidenceillustrates that the polymerization is indeed initiated by TiCl_4 in combination with HCl resulting fromhydrolysis by adventitious water.     

Study on controlled/living free-radical polymerization of methyl acrylate in the presence of benzyl 9H-carbazole-9-carbodithioate under thermal condition

The polymerizations of methyl acrylate have been studied under thermal condition using benzyl 9H-carbazole-9-carbodithioate (BCCDT) as control agent. The obtained polymers were characterized by gel permeation chromatography (GPC), ¹H nuclear magnetic resonance (¹H NMR) and MALDI-TOF mass spectra. The results at 60 °C show that the molecular weight of the polymer increases linearly with monomer conversion, the molecular weight distribution is fairly narrow (even inferior to 1.10), and there exists a linear relationship between ln ([M]₀/[M]) and polymerization time. It is worthy of being noticed that the narrow polydispersities are comparable with those from living anionic polymerization. All of the evidences indicate that the polymerization is a good ‘living’ process. When the experiment is carried out at higher temperature, the polymerization rate is markedly faster with controlled polymerization characters except for a relatively broader polydispersity. The good control for free radical polymerization may be correlated with the large conjugation structure of carbazyl of BCCDT.     

Catalyseurs Zieger-Natta supportés sur MgCl2 pour la polymérisation stéréorégulée du propène. II. Système catalytique simple: Solide binaire MgCl2-TiCl4 et solution cocatalytique triéthylaluminium,benzoate d'ethyle

The kinetics of propene polymerization in heptane slurry at 1–4 bars was studied with a catalytic system that consisted of a solid catalyst prepared by adsorption of TiCI₄ on pure porous MgCl₂ (by dehydrating MgCl₂, 6 H₂O with thionyl chloride) and a cocatalytic, heptanic solution of ethylbenzoate (BE) and triethylaluminium (TEA). At a temperature approaching 60°C/polymerization began immediately after the introduction of the monomer. The polymerization rate decreased continuously during the reaction. The loss in activity, however, was not due to a diffusional effect (e.g., blocking of the catalyst by the growing polymer). Studies of the ageing of the catalytic system showed a deactivation of the catalytic system itself as a function of the time of contact between the catalyst and the cocatalyst. The product of the thermal decomposition of the complex 1:2 formed by the reaction of BE with TEA was not associated with the deactivation process or stereospecific control, which depend on the BE/AI ratio and the presence of the complex.