Titanium complexes of dialkanolamine ligands as initiators for living ring‐opening polymerization of ε‐caprolactone

The titanium complexes with one ( 1a , 1b , 1c ) and two ( 2a , 2b ) dialkanolamine ligands were used as initiators in the ring‐opening polymerization (ROP) of ε‐caprolactone. Titanocanes 1a and 1b initiated living ROP of ε‐caprolactone affording polymers whose number‐average molecular weights (M_n) increased in direct proportion to monomer conversion (M_n ≤ 30,000 g mol^?1) in agreement with calculated values, and were inversely proportional to initiator concentration, while the molecular weight distribution stayed narrow throughout the polymerization (M_w/M_n ≤ 1.2 up to 80% monomer conversion). ¹H‐NMR and MALDI‐TOF‐MS studies of the obtained poly(ε‐caprolactone)s revealed the presence of an isopropoxy group originated from the initiator at the polymer termini, indicating that the polymerization takes place exclusively at the Ti–OⁱPr bond of the catalyst. The higher molecular weight polymers (M_n ≤ 70,000 g mol^?1) with reasonable MWD (M_w/M_n ≤ 1.6) were synthesized by living ROP of ε‐caprolactone using spirobititanocanes ( 2a , 2b ) and titanocane 1c as initiators. The latter catalysts, according MALDI‐TOF‐MS data, afford poly(ε‐caprolactone)s with almost equal content of α,ω‐dihydroxyl‐ and α‐hydroxyl‐ω(carboxylic acid)‐terminated chains arising due to monomer insertion into “Ti–O” bond of dialkanolamine ligand and from initiation via traces of water, respectively. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1230–1240, 2010     

Living ring-opening polymerization of cyclic thiocarbonate

This work deals with the cationic ring-opening polymerization of a cyclic thiocarbonate, 5,5-dimethyl-1,3-dioxane-2-thione (1). The polymerization was carried out with 2 mol% of trifluoromethanesulfonic acid, methyl trifluoromethanesulfonate, boron trifluoride etherate, or triethyloxonium tetrafluoroborate as an initiator to afford the polythiocarbonate with the narrow molecular weight distribution (M_n = 11200-31000, M_w/M_n = 1.04-1.15). The molecular weight of the obtained polymer could be controlled by the feed ratio of the monomer to the initiator and increased when the second monomer was added to the polymerization mixture after quantitative consumption of 1 in the first stage, supporting that the cationic ring-opening polymerization of 1 proceeded via a living process.     

Atom Transfer Radical Polymerization of Styrene with 5‐Chloromethyl‐2‐hydroxy‐benzaldehyde as Initiator

Abstract

Atom transfer radical polymerization (ATRP) of styrene (St) proceeded using 5‐chloromethyl‐2‐hydroxy‐benzaldehyde as initiator, CuCl as catalyst, and N,N,N′,N′,N′‐pentamethyldiethyltriamine (PMDETA) as ligand. The results show that the polymerization is a first order reaction with respect to monomer concentration. The polymerization displayed living character as evidenced by a liner increase of monomer weight with conversation and a relatively narrow distribution (M _n/M _w ranges from 1.25 to 1.50). The end structure of PSt was analyzed by ¹H‐NMR, and PSt initiated MMA to form block copolymer (PSt‐b‐PMMA), which also proved that the polymerization could be controlled. The effects of reaction temperature and monomer to initiator mole ratio on the polymerization displayed living character were discussed.     

Controlled cationic polymerization of cyclopentadiene with B(C6F5)3 as a coinitiator in the presence of water

The controlled cationic polymerization of cyclopentadiene (CPD) at 20 °C using 1‐(4‐methoxyphenyl)ethanol (1)/B(C₆F₅)₃ initiating system in the presence of fairly large amount of water is reported. The number–average molecular weights of the obtained polymers increased in direct proportion to monomer conversion in agreement with calculated values and were inversely proportional to initiator concentration, while the molecular weight distribution slightly broadened during the polymerization (M_w/M_n ～ 1.15–1.60). ¹H NMR analyses confirmed that the polymerization proceeds via reversible activation of the C? OH bond derived from the initiator to generate the growing cationic species, although some loss of hydroxyl functionality happened in the course of the polymerization. It was also shown that the enchainment in cationic polymerization of CPD was affected by the nature of the solvent(s): for instance, polymers with high regioselectivity ([1,4] up to 70%) were obtained in acetonitrile, whereas lower values (around 60%) were found in CH₂Cl₂/CH₃CN mixtures. Aqueous suspension polymerization of CPD using the same initiating system was successfully performed and allowed to synthesize primarily hydroxyl‐terminated oligomers (F_n = 0.8–0.9) with M_n ≤ 1000 g mol^?1 and broad MWD (M_w/M_n ～ 2.2). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4734–4747, 2008     

Copolymerization of Chloroprene with Methyl Methacrylate by the EtnAICI3.n (n=1, 1.5, 2)-Vanadium Compound System

Abstract

The copolymerization of chloroprene with methyl methacrylate was studied in the presence of Et_n A1C1_3-n (n=1, 1.5, 2)-vanadium compounds. Monomer reactivity ratios in various catalyst concentrations were compared with that of a usual radical initiator. The apparent monomer reactivity ratio changed with the concentration of alkylaluminum halide. In this polymerization, alternating copolymer could not be prepared by the ordinary catalyst concentration by which the alternating copolymerization of chloroprene with acrylonitrile was carried out. The addition of more than 10 mole % of the alkylaluminum halide based on two monomers was required to prepare the copolymer which had equimolar composition irrespective of the feed monomer ratio.

The configuration in the repeating unit of the copolymer was discussed by comparison with the NMR and IR spectra of the radical copolymer and the cyclic Diels-Alder adduct of chloroprene-methyl methacrylate. The high alternating tendency was clarified by ozonolysis of the copolymer which was prepared under the conditions which produced equimolar copolymer in various feed monomer ratios. The chloroprene unit of the copolymer was present in the 1, 4-trans structure in the copolymer prepared by the Et_n A1C1_3-n -vanadium compound system.     

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     

丙烯酰胺在离子液体中的原子转移自由基聚合

在1-丁基-3-甲基咪唑四氟硼酸盐离子液体中以氯化苄为引发剂,氯化亚铜/2,2’-联吡啶为催化剂成功实现了丙烯酰胺的原子转移自由基聚合(ATRP)。用IR对聚合物的结构进行了表征,证实聚合物链端具有-Cl端基。考察了引发剂用量、催化剂和配体用量、单体用量和反应时间等因素对丙烯酰胺在离子液体中的原子转移自由基聚合的影响,结果表明,反应时间为1.5 h时转化率达到31.43%,M_n^GPC=4451,M_w/M_n=1.38。且80 ℃下丙烯酰胺在离子液体中的最佳聚合工艺条件为：单体浓度3 mol/L,引发剂浓度0.010 mol/L,催化剂浓度0.015 mol/L,反应时间1 h。     

Schiff base as a novel kind of catalyst for reversible complexation‐mediated radical polymerization of methyl methacrylate

Two kinds of Schiff base, N,N′‐dibenzylidene‐1,2‐diaminoethane (NDBE) and N,N′‐disalicylidene‐1,2‐diaminoethane, have been found as efficient organic catalyst for reversible complexation‐mediated radical polymerization (RCMP) of methyl methacrylate (MMA) for the first time. The polymerization results show obvious features of “living”/controlled radical polymerization. Well‐defined and low‐polydispersity polymers (M_w/M_n = 1.20–1.40) are obtained in RCMP of MMA catalyzed by Schiff base at mild temperature (65–80°C). Moreover, Schiff base also exhibits a particularly high reactivity for RCMP of MMA with in situ formed alkyl iodide initiator. The polymer molecular weight and its polydispersity (M_w/M_n is around 1.20) are well controlled even with high monomer conversion. Notably, when the dosage of azo initiator is same as the dosage of iodine, the polymerization could also be realized in the presence of NDBE. The living feature of synthesized polymer is confirmed through the chain extension experiment. In short, Schiff base is a kind of high‐efficient catalyst for RCMP and reverse RCMP of MMA, which can be one of the most powerful and robust techniques for polymer synthesis. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1653–1663     

Group 4 complexes bearing bis(salphen) ligands: Synthesis,characterization, and polymerization studies

Six different complexes containing bis(salphen) [salphen = N,N'‐phenylenebis(salicylideneimine)] ligands were synthesized and characterized by various spectroscopic techniques and elemental analysis. In the presence of benzyl alcohol as an initiator, all the complexes catalyze the ring‐opening polymerization of lactide and ε‐caprolactone, generating high molecular weight (M_n) polymers in a controlled fashion. The linear relationship between the % conversion and M_n proved the control over the polymerization process. The presence of OBn group as an end group was confirmed by MALDI‐TOF and ¹H NMR spectral analysis of low M_n oligomers. The polymerization followed first‐order kinetics as revealed by kinetic experiments. All the complexes were good precatalysts for the polymerization of ethylene. The effect of temperature and time on the yield and activity toward the polymerization of ethylene were widely investigated. In addition, in the presence of tetrabutylammonium bromide as cocatalyst, the formation of degradable polycarbonate with moderate M_n value and narrow molecular weight distributions was observed by the copolymerization of cyclohexene oxide with CO₂. The effect of initiator structure, temperature, CO₂ pressure, catalyst/cocatalyst loading on the activity, and selectivity toward copolymerization were systematically examined. The thermal properties of the copolymer synthesized were explored using differential scanning calorimetric and thermogravimetric analysis. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 809–824     

A novel azo‐containing dithiocarbamate used for living radical polymerization of methyl acrylate and styrene

A novel azo‐containing dithiocarbamate, 1‐phenylethyl N,N‐(4‐phenylazo) phenylphenyldithiocarbamate (PPADC), was successfully synthesized and used to mediate the polymerization of methyl acrylate (MA) and styrene (St). In the presence of PPADC, the reversible addition‐fragmentation chain transfer (RAFT) polymerization was well controlled in the case of MA, however, the slightly ill‐controlled in the case of St. Interestingly, the polymerization of St could be well‐controlled when using PPADC as the initiator in the presence of CuBr/PMDETA via atom transfer radical polymerization (ATRP) technique. In the cases of RAFT polymerization of MA and ATRP of St, the kinetic plots were both of first‐order, and the molecular weight of the polymer increased linearly with the monomer conversion while keeping the relatively narrow molecular weight distribution (M_w/M_n). The molecular weight of the polymer measured by gel permeation chromatographer (GPC) was also close to the theoretical value (M_n(th)). The obtained polymer was characterized by ¹H‐NMR analysis, ultraviolet absorption, FTIR spectra analysis and chain‐extension experiments. Furthermore, the photoresponsive behaviors of azobenzene‐terminated poly(methyl acrylate) (PMA) and polystyrene (PS) were similar to PPADC. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5626–5637, 2008     

Radical polymerization of butadiene-1-carboxylic acid

The homopolymerization and copolymerization of butadiene-1-carboxylic acid (Bu-1-Acid) (M₁) were studied in tetrahydrofuran at 50°C with azobisisobutyronitrile as an initiator. The initial rate of polymerization was proportional to [AIBN]^1/2 and [Bu-1-Acid]¹. The overall activation energy for the polymerization was 22.87 kcal/mole. For copolymerization with styrene (M₂) and acrylonitrile (M₂), the monomer reactivity ratios r₁, r₂ were determined by the Fineman-Ross method, as follows; r₁ = 5.55, r₂ = 0.08 (M₂ = styrene); r₁ = 11.0, r₂ = 0.03 (M₂ = acrylonitrile). Alfrey-Price Q-e values calculated from these values were 6.0 and +0.11, respectively. The Bu-1-Acid unit in the copolymer as well as the homopolymer was found from infrared and NMR spectral analyses to be composed of a trans-1,4 bond. The hydrogen-transfer polymerization of Bu-1-Acid leading to polyester was attempted with triphenylphosphine as initiator, but did not occur.     

Anionic polymerization of acrylates. II. Polymerization of 2-ethylhexyl acrylate initiated by butyllithium/lithium-tert-butoxide system in tetrahydrofuran and its mixtures with toluene

The anionic polymerization of 2-ethylhexyl acrylate (EtHA) initiated with the complex butyllithium/lithium-tert-butoxide (BuLi/t-BuOLi) was investigated at ?60°C in a medium of various solvating power, i.e., in mixtures of toluene and tetrahydrofuran and in neat tetrahydrofuran. With increasing amount of THF in the mixture the attainable limiting conversion of polymerization decreases; the monomer can be polymerized quantitatively only in a toluene/THF mixture (9/1). Molecular weights of the polymers thus obtained, their distribution, and initiator efficiency are not appreciably affected by the polymerization medium. The molecular weight distribution of the products is medium-broad (M_w/M_n = 2–2.4), with a hint of bimodality. The ¹H-¹³C-NMR, and IR spectra suggest that during the polymerization there is neither any perceptible reesterification of the polymer with the alkoxide nor transmetalation of the monomer with the initiator. In a suitable medium, autotermination of propagation proceeds to a limited extent only, predominantly via intramolecular cyclization of propagating chains; in a medium with a higher content of polar THF, it prevails and terminates propagation before the polymerization of the monomer has been completed. © 1992 John Wiley & Sons, Inc.     

Synthesis and characterization of poly(ethylene glycol) diacrylate copolymers containing azobenzene groups prepared by frontal polymerization

A novel polymer matrix containing amino–nitro substituted azobenzene groups was obtained by frontal polymerization. (E)‐2‐(Ethyl(4‐((4‐nitrophenyl)diazenyl)phenyl)amino)ethyl methacrylate (MDR‐1) was copolymerized with poly(ethylene glycol) diacrylate (PEGDA) using this easy and fast polymerization technique. The effect of the amount of the incorporated azo‐monomer into the polymer matrix was studied in detail and correlated to front velocity, maximum temperature, initiator concentration, and monomer conversion. The obtained materials were characterized by infrared spectroscopy (Fourier transform infrared), and their thermal properties were studied by thermogravimetric analysis and differential scanning calorimetry. Moreover, the optical properties of the polymers were studied by absorption spectroscopy in the UV–Vis region. Absorption spectra of the copolymers exhibit a significant blue shift of the absorption bands with respect to the azo‐monomer, due to the presence of H‐aggregates. Cubic nonlinear optical (NLO) characterizations of the PEGDA/MDR‐1 copolymers were performed according to the Z‐Scan technique. It has been proven that samples with higher MDR‐1 content (0.75 mol %) exhibited outstandingly high NLO‐activity with negative NLO‐refractive coefficients in the promising range of n₂ = ?8.057 × 10^?4 esu. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Aqueous MADIX/RAFT polymerization of diallyldimethylammonium chloride: Extension to the synthesis of poly(DADMAC)‐based double hydrophilic block copolymers

Macromolecular design by interchange of xanthates/reversible addition fragmentation chain transfer polymerization (MADIX/RAFT) of diallyldimethylammonium chloride (DADMAC) using the hydrophobic O‐ethyl‐S‐(1‐methoxycarbonyl) ethyl dithiocarbonate MADIX/RAFT mediating agent, Rhodixan A1, was investigated. Attempts to obtain an efficient control of DADMAC polymerization in a water/ethanol mixture failed because of significant chain transfer to ethanol. The use of a water‐soluble Rhodixan A1‐terminated acrylamide oligomer as the MADIX/RAFT agent enabled the controlled polymerization of DADMAC in water at 50 °C using the cationic azo initiator V‐50. An excellent agreement was found between experimental and theoretical M_n values throughout polymerization and over a broad range of initial concentration of xanthate. Polydispersity indexes (PDIs) at the end of the polymerization were abnormally high for a process showing a linear increase of M_n with monomer conversion (1.8 < PDI < 2.0). This feature was explained by the measurement of a high transfer constant to xanthate (C_x = 18.8 ± 1.6) but a low interchange transfer constant (C_ex = 1.5). Nevertheless, poly(acrylamide)–poly(DADMAC) double hydrophilic block copolymers (DHBCs) of controlled M_n and composition could be successfully synthesized for the first time. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Synthesis and Characterization of Four-Arm Star Poly(ϵ-caprolactone)-Block-Poly(cyclic-carbonate methacrylate) Copolymers by Combining Ring-Opening Polymerization With Atom Transfer Radical Polymerization

Well-defined four-arm star poly(?-caprolactone)-block-poly(cyclic carbonate methacrylate) (PCL-b-PCCMA) copolymers were synthesized by combining ring-opening polymerization (ROP) with atom transfer radical polymerization (ATRP). First, a four-arm poly(?-caprolactone) (PCL) macroinitiator [(PCL-Br)₄] was prepared by the ROP of ?-CL catalyzed by stannous octoate at 110°C in the presence of pentaerythritol as the tetrafunctional initiator followed by esterification with 2-bromoisobutyryl bromide. The sequential ATRP of CCMA monomer was carried out by using the (PCL-Br)₄ tetrafunctional macroinitiator (MI) and in the presence of CuBr/2, 2′-bipyridyl system in DMF at 80°C with [(MI)]:[CuBr]:[bipyridyl] = 1:1:3 to yield block polymers with controlled molecular weights (M_n (NMR) = 10700 to 27300 g/mol) by varying block lengths and with moderately narrow polydispersities (M_w/M_n = 1.2–1.4). Block copolymers with different PCL: PCCMA copolymer composition such as 50:50, 70:30 and 74:26 were prepared with good yields (48-74%). All these block copolymers were well characterized by NMR, FTIR and GPC and tested their thermal properties by DSC and TGA.     

Living cationic polymerization of isobutyl vinyl ether by the carboxyl group of the carbon black/zinc chloride initiating system

The effect of zinc chloride (ZnCl₂) on the cationic polymerization of isobutyl vinyl ether (IBVE) initiated by carboxyl groups on a carbon black surface was investigated. Although the polymerization of IBVE was initiated by carboxyl groups on the surface, the rate of polymerization was small and the molecular weight distribution (MWD) of poly IBVE was very broad. The rate of the polymerization was found to be drastically increased, and 100% monomer conversion was achieved in a short time by the addition of ZnCl₂. The number-average molecular weights (M_n) of the polyIBVE were directly proportional to monomer conversion in the polymerization initiated by the carbon black/ZnCl₂ system. By addition of the monomer at the end of the first-stage polymerization, the added monomer was smoothly polymerized at the same rate as in the first stage. The M_n of the polymer was in excellent agreement with the calculated value, assuming the polyIBVE chain forms per unit carboxyl group on the surface and MWD was narrow (M_w/M_n = 1.2 ～ 1.3). Based on the results, it is concluded that carbon black/ZnCl₂ system has an ability to initiate the living cationic polymerization of IBVE. Furthermore, it was found that polyIBVE was grafted onto the carbon black surface after the quenching of the living polymer with methanol. © 1995 John Wiley & Sons, Inc.     

Atom Transfer Radical Polymerization of Styrene Using Multifunctional Iniferter Reagents as Initiators

Summary: Two multifunctional iniferters, 1,4-bis-(α-N,N-diethyldithiocarbamyl-isobutyryloxy)-benzene (BDCIB) and 1,3,5-tris-(α-N,N-diethyldithiocarbamyl-isobutyryloxy)-benzene (TDCIB), were successfully synthesized and used as initiators to initiate the polymerization of styrene in the presence of a CuBr/PMDETA complex. The polymerization results demonstrated that the kinetic plots in all cases were first-order to the monomer, the molecular weight of the polymers increased linearly with the monomer conversion; meanwhile, the molecular weight distribution of the polymer was kept to a very low value (M_w/M_n ≤ 1.35). Furthermore, the measured molecular weights were very close to the calculated values, which indicated the high efficiency of the initiator for the polymerization of styrene. The effect of catalyst concentration and initiator concentration was not obvious and the influence of polymerization temperature was apparent, and the polymerization rate increased with the polymerization temperature. The results of chain-extension and ¹H NMR analysis proved that the polymer obtained was capped with diethylthiocarbamoylthiy (DC) group.     

Organocuprates as Initiators for Methyl Methacrylate Polymerization

Abstract

Polymerizations of methyl methacrylate initiated by organocuprates in tetrahydrofuran solution have been investigated. The heterocuprate lithium n-butylcyanocuprate was found to be an effective initiator at - 78°C, and lithium di-n-butylcuprate was confirmed as an effective initiator; both species give rapid polymerization to virtually complete conversion of monomer. Polydispersities (M_w/M_n ) are about 1.5. Polymerizations have an inherent termination reaction and a low initiator efficiency. Polymerization of methyl vinyl ketone is virtually uncontrollable, and polymerizations of methyl methacrylate are inhibited by styrene.     

Organoaluminum‐mediated polymerization of diazoketones

Polymerization of diazoketones mediated by organoaluminum compounds was investigated. Trialkylaluminum R₃Al (R = iBu, Et, Me) and diisobutylaluminum hydride (DIBAL) polymerized (E)‐1‐diazo‐3‐nonen‐2‐one ( 1 ) to give polymers with M_n = 2000–3500, which contained nearly 33 mol % of azo group (? N?N? ) along with the dominant acylmethylene unit in the main chain. On the other hand, when (E)‐1‐diazo‐4‐phenyl‐3‐buten‐2‐one ( 2 ) was used as a monomer for the organoaluminum‐mediated polymerization, the resulting polymers had ethylidene (? CH[CH₃]? ) units in the main chain along with acylmethylene and azo group, as a result of reductive cleavage of the acyl group during the polymerization. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5209–5214, 2007     

9‐Bromoanthracene photodimers as initiators in controlled radical polymerization: Silane radical atom abstraction coupled with nitroxide mediated polymerization

Slow initiation relative to propagation has previously prevented photodimers of 9‐bromoanthracene or 9‐chloroanthracene, formed by [4 + 4] photocyclization reactions of the analogous 9‐haloanthracene, from being viable initiators in atom transfer radical polymerization (ATRP) reactions. The resulting polymers were found to possess high polydispersity index (PDI) values, much higher than expected number average molecular weight (M_n) values, with the reaction displaying a nonlinear relationship between monomer conversion and M_n. We report here the use of silane radical atom abstraction (SRAA) to create initiating bridgehead radicals in the presence of 2,2,6,6‐tetramethylpiperidine‐1‐oxyl (TEMPO) to mediate the polymerization. When using SRAA coupled with nitroxide mediated polymerization, a dramatic decrease in PDI values was observed compared with analogous ATRP reactions, with M_n values much closer to those anticipated based on monomer‐to‐initiator ratios. Analysis using UV‐Vis spectroscopy indicated only partial anthracene labeling (～ 25%) on the polymers, consistent with thermolysis of the anthracene photodimer coupled with competition between initiation from the bridgehead photodimer radical and silane‐based radical. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6016–6022, 2008