共轭双烯与丙烯酸甲酯交替共聚物的~(13)C-NMR谱研究

用~(13)C-NMR方法研究了丁二烯(BD)-丙烯酸甲酯(MA)、异戊二烯(IP)-MA和氯丁二烯(CP)-MA交替共聚物(分别简称为PBM、PIM和PCM)的联接方式和微观结构。在PBM中,BD单元以反-1,4-结构存在,并有少量的顺-1,4-和1,2-结构,其比例为88:7:5;在PIM和PCM中,IP与CP单元也主要以反-1,4-结构存在,与MA以“头-头”方式相连接。在PCM中还有少量CP-CP相连接的结构,交替度较低,而PBM和PIM则完全是交替结构。     

Donor-acceptor complexes in copolymerization. L. Preparation and microstructure of chlorine-containing alternating conjugated diene–acceptor monomer copolymers

Neighboring monomer units cause significant shifts in the infrared absorption peaks attributed to cis- and trans-1,4 units in conjugated diene-acceptor monomer copolymers. Conjugated diene-maleic anhydride alternating copolymers apparently have a predominantly cis-1,4-structure, while alternating diene-SO₂ copolymers have a predominantly trans-1,4 structure. Alternating copolymers of butadiene, isoprene, and pentadiene-1,3 with α-chloroacrylonitrile and methyl α-chloroacrylate, prepared in the presence of Et_1.5AlCl_1.5(EASC), have trans-1,4 unsaturation. Alternating copolymers of chloroprene with acrylonitrile, methyl acrylate, methyl methacrylate, α-chloroacrylonitrile, and methyl α-chloroacrylate prepared in the presence of EASC-VOCl₃ have trans-1,4 configuration. The reaction between chloroprene and acrylonitrile in the presence of AlCl₃ yields the cyclic Diel-Alder adduct in the dark and the alternating copolymer under ultraviolet irradiation. The equimolar, presumably alternating, copolymers of chloroprene with methyl acrylate and methyl methacrylate undergo cyclization at 205°C to a far lesser extent than theoretically calculated, to yield five and seven-membered lactones. The polymerization of chloroprene in the presence of EASC and acetonitrile yields a radical homopolymer with trans-1,4 unsaturation.     

Copolymerization of dienes with neodymium tricarboxylate-based catalysts and cis-polymerization mechanism of dienes

It was found that poly(butadiene), poly(isoprene), and poly(2,3-dimethylbutadiene) with high cis-1,4 content were obtained with Nd(OCOR)₃–(i-Bu)₃Al–Et₂AlCl catalysts (R = CF₃, CCl₃, CHCl₂, CH₂Cl, CH₃) in hexane at 50°C [cis-1,4 content: poly(BD), > 98%; poly(IP), ≥ 96%; poly(DMBD), ≥ 94%]. Copolymerization of IP and styrene (St) was carried out at various monomer feed ratios to evaluate the monomer reactivity ratio and cis-1,4 content of the diene unit and then to elucidate the cis-1,4 polymerization mechanism of IP. The cis-1,4 content of the IP unit in the copolymers decreased with increasing St content in the copolymers. The cis-1,4 polymerization was disturbed by incorporating St unit in the copolymers, since the penultimate St unit hardly coordinates to the neodymium metal, resulting in a decrease of the cis-1,4 content in the copolymers. That is, the cis-1,4 polymerization of IP is suggested to be controlled by a back-biting coordination of the penultimate diene unit. On the other hand, in the case of poly(BD-co-IP) and poly(BD-co-DMBD), the cis-1,4 content of the BD, IP, and DMBD units in the copolymers was almost constant (cis: 94–98%), irrespective of the monomer feed ratios and polymerization temperature. Consequently, the penultimate IP and DMBD units favorably control the terminal BD, IP, or DMBD unit to the cis-1,4 configuration through the back-biting coordination. For the monomer reactivity ratios, a clear difference was observed in each system: r_BD = 1.22, r_IP = 1.14; r_BD = 40.9, r_DMBD = 0.15. Low polymerizability of DMBD was mainly ascribed to the steric effect of the methyl substituents. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1707–1716, 1998     

Copolymerization of propylene with 1,3‐butadiene using isospecific zirconocene catalysts

Poly(propylene‐ran‐1,3‐butadiene) was synthesized using isospecific zirconocene catalysts and converted to telechelic isotactic polypropylene by metathesis degradation with ethylene. The copolymers obtained with isospecific C₂‐symmetric zirconocene catalysts activated with modified methylaluminoxane (MMAO) had 1,4‐inserted butadiene units ( 1,4‐BD ) and 1,2‐inserted units ( 1,2‐BD ) in the isotactic polypropylene chain. The selectivity of butadiene towards 1,4‐BD incorporation was high up to 95% using rac‐dimethylsilylbis(1‐indenyl)zirconium dichloride (Cat‐A)/MMAO. The molar ratio of propylene to butadiene in the feed regulated the number‐average molecular weight (M_n) and the butadiene contents of the polymer produced. Metathesis degradations of the copolymer with ethylene were conducted with a WCI₆/SnMe₄/propyl acetate catalyst system. The ¹H NMR spectra before and after the degradation indicated that the polymers degraded by ethylene had vinyl groups at both chain ends in high selectivity. The analysis of the chain scission products clarified the chain end structures of the poly(propylene‐ran‐1,3‐butadiene). © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5731–5740, 2007     

Polymérisation radicalaire du pentadiène-1,3. II. Microstructure des résidus pentadiéniques dans les homo- et copolymères des cis et trans pentadiènes-1,3 avec l'acrylonitrile

The microstructure of diene units was investigated in radical homopolymers of the cis and trans isomers of 1,3-pentadiene and copolymers with acrylonitrile, synthetized in bulk and emulsion. Experiments were carried out by infrared spectroscopy, 100 MHz ¹H-NMR, and 25 MHz ¹³C-NMR studies. No difference between the bulk and emulsion samples was noted. The microstructure of poly(1,3-pentadiene) is practically independent of the cis or trans configuration of the diene monomer and is as follows: 56–59% trans-1,4, 15–17% cis-1,4, 16–20% trans-1,2 7–10% cis-1,2 and 0% 3,4. On the other hand, up to about 30% of incorporated acrylonitrile (10% in the feed), the microstructure of the pentadiene fraction in the copolymers is not affected. This finding suggests that the penultimate unit has very little influence on the polymerization process involving the terminal pentadienly unit. Beyond 10% of acrylonitrile in the feed, the proportions of the structural units were linearly dependent upon the acrylonitrile content: trans-1,4 content increased whereas the amounts of cis-1,4 trans-1,2 and cis-1,2 decreased (except the cis-1,2 fraction, constant in the copolymers from the cis-diene). These results are discussed on the assumption that the microstructure of pentadiene residues is strongly associated with the acrylonitrile comonomer in the feed.     

COPOLYMERIZATION OF BUTADIENE AND ISOPRENE CATALYZED BY V(acac)_3-Al(i-Bu)_2Cl-Al_2Et_3Cl_3 CATALYST AND CHARACTERIZATION OF THE PRODUCTS

Copolymerization of butadiene and isoprene catalyzed by the catalyst system V(acac)_3-Al(i-Bu)_2Cl-Al_2Et_3Cl_3 has been studied. Composition, microstructure, crystallinity and melting point of the copolymer obtained were determined by PGC, IR, X-ray diffraction and DSC methods respectively. The results revealed that the product was a copolymer and not a blend. The butadiene units presented in the copolymer were of trans-1,4-configuration, while the isoprene units were of both trans-1,4-and 3,4-forms. The melting point and crystallinity of the copolymer decrcascd with increase of molar ratio of isoprene to hutadiene.     

Comprehensive structural characterization of polyisoprene synthesized via cationic mechanism

The microstructure of polyisoprene synthesized with ^tBuCl/TiCl₄ initiating system is investigated using 1D and 2D (HSQC and HMBC) NMR spectroscopy. It is found that trans‐1,4‐units with regular (head‐to‐tail) and inverse (tail‐to‐tail) and (head‐to‐head) enchainments are predominant structures of unsaturated part of polymer chain, while 1,2‐ and 3,4‐units are presented in minor amounts. The new methodology for the quantitative calculation of the content of different structural units in polyisoprene chain including both types of inverse trans‐1,4‐addition (tail‐to‐tail and head‐to‐head) is proposed. It is shown that head groups consist of tert‐butyl group connected to trans‐1,4‐unit of polyisoprene chain. In addition, two types of chlorine‐containing end groups are found (trans‐4,1‐Cl and 4,3‐Cl), while conjugated double bonds at the chain end are totally absent. The methodology for the calculation of number‐average functionality by tert‐butyl head and chlorine end groups, respectively, is developed. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2430–2442     

Polymerizations of butadiene,isoprene, and 2,3-dimethylbutadiene by Gd(OCOCCl3)3–(i-Bu)3Al–Et2AlCl and the cis polymerization mechanism for dienes

Homopolymerizations of butadiene (BD), isoprene (IP), and 2,3-dimethylbutadiene (DMBD) were carried out by a Gd(OCOCCl₃)₃-based catalyst, to investigate the effects of the energy levels of the monomers or the sterical factor of the methyl substituents on the polymerizability and the cis-selectivity of the monomers. The order of the polymerizability at 50°C was as follows: BD (4.5 kg of polymer/(mol of Gd h)) ∼ IP (4.8) > DMBD (0.6). On the other hand, the cis-selectivity of the polymers was as follows: BD (98%) > IP (94%) > DMBD (35%). These results suggest that the terminal BD and IP units are controlled by the cis configuration by the coordination between the penultimate cis-vinylene unit and the catalyst metal, whereas the penultimate DMBD unit unfavorably controls the terminal DMBD unit to the cis-1,4 configuration through the back-biting coordination with difficulty by two methyl substituents compared with the penultimate BD and IP units. The validity of the back-biting coordination was examined by MO calculation with σ-allylnickel complexes. According to the formation energy with respect to the BD–BD diad, the cis–cis form is somewhat preferable to the trans–cis form through the coordination of the penultimate BD unit by ΔE = 0.028 au (ca. 17.6 kcal/mol). © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2283–2290, 1998     

Copolymerization of isoprene with ethylene catalyzed by cationic half‐sandwich fluorenyl scandium catalysts

Isoprene polymerization and copolymerization with ethylene can be carried out by using cationic half‐sandwich fluorenyl scandium catalysts in situ generated from half‐sandwich fluorenyl scandium dialkyl complexes Flu'Sc(CH₂SiMe₃)₂(THF)_n, activator, and AlⁱBu₃ under mild conditions. In the isoprene polymerization, all of these cationic half‐sandwich fluorenyl scandium catalysts exhibit high activities (up to 1.89 × 10⁷ g/mol_Sc h) and mainly cis?1,4 selectivities (up to 93%) under similar conditions. In contrast, these catalysts showed different activities and regio‐/stereoselectivities being significantly dependent on the substituents of the fluorenyl ligands in the copolymerization of isoprene with ethylene under an atmosphere of ethylene (1 atm) at room temperature, affording the random copolymers with a wide range of cis?1,4‐isoprene contents (IP content: 64 ? 97%, cis?1,4‐IP units: 65 ? 79%) or almost alternating copolymers containing mainly 3,4‐IP‐alt‐E or/and cis?1,4‐IP‐alt‐E sequences. Moreover, novel high performance polymers have been prepared via selective epoxidation of the vinyl groups of the 1,4‐isoprene units in the IP‐E copolymers. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2898–2907     

Synthesis of poly(dimethylsiloxane)‐containing diblock and triblock copolymers by the combination of anionic ring‐opening polymerization of hexamethylcyclotrisiloxane and nitroxide‐mediated radical polymerization of methyl acrylate,isoprene, and styrene

Poly(dimethylsiloxane)‐containing diblock and triblock copolymers were prepared by the combination of anionic ring‐opening polymerization (AROP) of hexamethylcyclotrisiloxane (D₃) and nitroxide‐mediated radical polymerization (NMRP) of methyl acrylate (MA), isoprene (IP), and styrene (St). The first step was the preparation of a TIPNO‐based alkoxyamine carrying a 4‐bromophenyl group. The alkoxyamine was then treated with Li powder in ether, and AROP of D₃ was carried out using the resulting lithiophenyl alkoxyamine at room temperature, giving functional poly(D₃) with M_w/M_n of 1.09–1.16. NMRPs of MA, St, and IP from the poly(D₃) at 120 °C gave poly(D₃‐b‐MA), poly(D₃‐b‐St), and poly(D₃‐b‐IP) diblock copolymers, and subsequent NMRPs of St from poly(D₃‐b‐MA) and poly(D₃‐b‐IP) at 120 °C gave poly(D₃‐b‐MA‐b‐St) and poly(D₃‐b‐IP‐b‐St) triblock copolymers. The poly(dimethylsiloxane)‐containing diblock and triblock copolymers were analyzed by ¹H NMR and size exclusion chromatography. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6153–6165, 2005     

A new insight into the mechanism of 1,3‐dienes cationic polymerization. II. Structure of poly(1,3‐pentadiene) synthesized with tBuCl/TiCl4 initiating system

The microstructure of poly(1,3‐pentadiene) synthesized by cationic polymerization of 1,3‐pentadiene with ^tBuCl/TiCl₄ initiating system is analyzed using one‐dimensional‐ and two‐dimensional‐NMR spectroscopy. It is shown that unsaturated part of chain contains only homo and mixed dyads with trans?1,4‐, trans?1,2‐, and cis?1,2‐structures with regular and inverse (head‐to‐head or tail‐to‐tail) enchainment, whereas cis?1,4‐ and 3,4‐units are totally absent. The new quantitative method for the calculation of content of different structural units in poly(1,3‐pentadiene)s based on the comparison of methyl region of ¹³C NMR spectra of original and hydrogenated polymer is proposed. The signals of tert‐butyl head and chloromethyl end groups are identified in a structure of poly(1,3‐pentadiene) chain and the new approaches for the quantitative calculation of number‐average functionality at the α‐ and ω‐end are proposed. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3297–3307     

Ethylene-butadiene copolymerization with three-component catalyst systems Al[N(CH3)2]3, Al(C2H5)Cl2 and vanadium chlorides

The ethylene butadiene copolymerization with systems of three components Al[N(CH₃)₂]₃, Al(C₂H₅)Cl₂ and VOCl₃ or VCl₄, is described. In the resulting copolymers, the butadiene units are substantially in trans-1,4 configuration. Although it is possible to obtain copolymers with a wide range of composition, attention was paid to products with a low content of unsaturation (less than 2% mole of butadiene). These copolymers are highly homogeneous. They show high crystallinity of the polyethylene type and they can be crosslinked with conventional sulphur recipes.     

Neodymium alk(aryl)oxides-dialkylmagnesium systems for butadiene polymerization and copolymerization with styrene and glycidyl methacrylate

The application of well-defined neodymium alkoxides/aryloxides in combination with dialkylmagnesium reagents for 1,3-butadiene (BD) polymerization and copolymerization with styrene (St) and glycidyl methacrylate (GMA) has been investigated. The trinuclear complex Nd₃(Ot-Bu)₉(THF)₂ (1) provided a low-activity system for BD polymerization, even at high temperature, but with a high trans-1,4 stereospecificity (trans-1,4≈95%). Aryloxide complexes Nd(O-2,6-t-Bu₂-4-Me-Ph)₃(THF) (2) and Nd(O-2,6-t-Bu₂-4-Me-Ph)₃ (3) were found to give more active systems. The polymerization displayed a controlled character, i.e. a precise control of the molecular weight and a low polydispersity (M_w/M_n<1.30) for high catalyst concentration, keeping the same level of stereocontrol over the polymerization course. The statistical copolymerization of BD and styrene with those systems was successful. High-molecular weight copolymers (M_n up to 50?000 g mol⁻¹) with noticeable styrene content (3-15 mol%) were synthesized. Determination of the microstructure by ¹³C-NMR showed exclusively trans-1,4-BD-St sequences. The livingness of BD polymerization encouraged attempts of diblock copolymerization with GMA. In this case, low-molecular weight polymers with variable polydispersities were obtained (M_n<20?000 g mol⁻¹; M_w/M_n=1.4-5.0). The composition of the copolymers was analyzed by ¹H- and ¹³C-NMR and IR spectroscopies. SEC analyses confirmed the true nature of the diblock copolymer. The influence of the alkylating agent on those (co)-polymerizations was briefly studied. Finally, the mechanism of polymerization is also discussed.     

Structural characterization of polybutadiene synthesized via cationic mechanism

The microstructure of polybutadiene synthesized via cationic polymerization using TiCl₄‐based initiating systems has been investigated using 1D (¹Н, ²Н, and ¹³С) and 2D (HSQC and HMBC) NMR spectroscopy. It was found that trans‐1,4‐unit is predominant structure of unsaturated part of polymer chain. Besides, the small amount of 1,2‐structures was also detected, while cis‐1,4‐units were totally absent. The signals of carbon atoms of three types of head groups (trans‐1,4‐, 1,2‐, and tert‐butyl) and two types of end groups (trans‐1,4‐Cl and 1,2‐Cl) were identified for the first time in macromolecules of cationic polybutadiene. It was showed that tert‐butyl head groups were formed due to the presence in monomer of admixtures of isobutylene. The new methodology for calculation of the content of different structural units in polybutadiene chain as well as the head and end groups was proposed. It was established that main part of 1,2‐units distributed randomly along the polybutadiene chain as separate units between trans‐1,4‐structures. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 387–398     

Alternating copolymerization of 2,4-dicyanobut-1-ene and isoprene: Structural analysis

The two monomers 2,4-dicyanobut-1-ene and isoprene undergo spontaneous copolymerization when mixed together. A more controlled set of solution copolymerizations have been carried out in toluene to low conversions (< 4%), and analysis of the data gave monomer reactivity ratios of r₁, (DCB) = 0.016 and r₂ (IP) = 0.109. Alternating copolymers are formed over a wide feed range, and the copolymer structure has been analyzed using ¹H, ¹³C-NMR and IR spectroscopy. This shows that the isoprene units are predominantly in the trans-1,4 conformation and are attached to the DCB through the 1 position when adding onto the chain. The presence of a 1:1 donor–acceptor complex has been identified in CCl₄, solutions of the monomers with an equilibrium quotient of K = 0.055 dm³ mol^?1 at 333 K. The frontier orbital approach has been used in an attempt to elucidate the most likely structure of the D-A complex.     

PREPARATION AND CHARACTERIZATION OF cis-,4-POLYBUTADIENE CONTAINING A FRACTION OF trans-1,4-POLYBUTADIENE

Polymerization of butadiene catalysed first with V(acac)_3-Al(i-Bu)_2Cl, then with Co(acac)_3-H_2O-Al(i-Bu)_2Cl has been studied. The polymer obtained was identified to be a new variety of cis-1,4-polybutadiene which contained a fraction of trans-1,4-polybutadiene chemically bonded to the cis-1,4-polybutadiene chains. Its molecular weight and trans-1,4 content can be regulated by varying the catalyst composition and concentration as well as other polymerization conditions. The trans-1,4 fraction, although it presents only in 9—16%, forms a crystalline phase in the matrix at room temperature and facilitates the crystallization of the polymer.     

Self-organizing silane-siloxane copolymers: Synthesis and behavior in the block and monomolecular layers

Trans tactic cyclolinear organosilicon copolymers with a regular alternation of decamethylcyclohexasiloxane and decamethylcyclosilane units have been synthesized by the heterofunctional polycondensation of trans-2,8-dihydroxydecamethylcyclohexasiloxane with 1,3-or 1,4-dichlorodecamethylcyclohexasilanes. The structure of the copolymers has been studied by ¹H and ²⁹Si NMR, and IR spectroscopy; molecular mass measurements; and elemental analysis. The phase behavior of these copolymers in the block has been examined by DSC, X-ray diffraction, and polarization optical microscopy. It has been demonstrated that the copolymers of interest may exist in the mesomorphic state within a wide temperature interval. The ability of cyclolinear organosilicon copolymers to spread at the water/air interface and to form monolayers has been investigated. It has been shown that cyclosilane units that are structural isomers affect the pattern of surface pressure isotherms of the said copolymers.     

Oxidation of Poly(2,3-dimethylbutadiene-1,3)

Abstract

Poly(2,3-dimethylbutadiene-1,3) containing cis-1,4, trans-1,4, and 1,2 structural units in various proportions undergoes rapid oxidation even at room temperature. The process of oxidation is accompanied by cyclization. The concentration of peroxides that form at room temperature is relatively very high, reaching the value of one peroxidic group per 16 monomeric units. The formation of six-membered rings involving the peroxidic bonds in poly(2,3-dimethylbutadiene) is accompanied by degradation.     

Glass transition temperature modification of acrylic and dienic type copolymers of 4-chloromethyl styrene with incorporation of (Me3Si)3C- groups

The new functional styrenic monomer, 4-trisylmethyl styrene (TsiMS) [Tsi=trisyl=tris(trimethylsilyl)methyl], was synthesized by reacting 4-chloromethyl styrene (CMS) with trisyllithium (TsiLi) in tetrahydrofuran (THF) solvent in the presence of copper chloride (CuCl). Attempt for the free radical polymerization of TsiMS by α,α^′-azobis(isobutyronitrile) (AIBN) as an initiator at 70 ± 1 °C failed for several periods of times. This result showed that the trisyl group is a highly sterically hindered substituent and, subsequently, TsiMS becomes resistant for polymerization. Therefore, for preparation of new methacrylic, acrylic and dienic copolymers of TsiMS, we firstly synthesized the copolymers of CMS with different monomers such as methyl methacrylate (MMA), ethyl methacrylate (EMA), methyl acrylate (MA), ethyl acrylate (EA), n-butyl acrylate (BA) and isoprene (IP) by free radical polymerization method in toluene solution at 70 ± 1 °C using AIBN initiator to give the copolymers I-VI in good yields. The copolymer compositions were obtained using related ¹H NMR spectra and the polydispersity indices of the copolymers determined using gel permeation chromatography (GPC). The trisyl groups were then covalently attached to the obtained copolymers as side chains by reaction between excess of TsiLi and benzyl chloride bonds of CMS units, to give the copolymers - in 80-92% yields. All the resulted polymers were characterized by FT-IR, ¹H NMR and ¹³C NMR spectroscopic techniques. The solubility of all the copolymers was examined in various polar and non-polar solvents. The glass transition temperature (T_g) of all copolymers was determined by differential scanning calorimetry (DSC) apparatus. The T_g value of copolymers containing bulky trisyl groups was found to increase with incorporation of trisyl groups in polymer structures. The presence of trisyl groups in polymer side chains, create new macromolecules with novel modified properties.     

Crystallization-induced reactions of copolymers. III. Ester interchange reorganization of poly(cis/trans-1,4-cyclohexylenedimethylene terephthalate)

Random copolymers of cis- and trans-1,4-cyclohexylenedimethylene terephthalate were permitted to undergo ester-interchange reorganization at temperatures just below the melting point. As predicted from the principles of crystallization-induced reactions of semicrystalline copolymers proposed in the first two papers of this series, the copolymers were observed to undergo changes in physical properties which are associated with the conversion of a random to a block copolymer. The driving force for this antiequilibrium ordering process is believed to be the irreversible expansion of the crystalline regions following replacement of cis by trans glycol units. Solubility, crystallinity, and crystallization properties were monitored to determine the effects of copolymer composition, temperature, catalyst, and molecular weight on the reorganization rate. This type of process is also believed to be responsible for the direct preparation of block copolymers by a solid-state polycondensation reaction used in this study.