Vinyl polymerization. 284. Polymerization of methyl methacrylate initiated by 4.4′-diazidoazobenzene

The kinetics of the radical polymerization of methyl methacrylate (MMA) with 4.4′-diazidoazobenzene (DAAB) as initiator was investigated in benzene solution. It was found that the initial rate of polymerization (R_p) can be expressed by the equation: The overall activation energy for the polymerization was estimated to be 20.5 kcal/mole. The polymer obtained by the polymerization of MMA initiated by the above initiator was found to contain azobenzene fragment, presumably as endgroup. The thermal decomposition of DAAB was also studied in the temperature range 110 to 130°C. The overall activation energy of the decomposition of DAAB was 35.2 kcal/mole. The polymerization mechanism is discussed on the basis of these results.     

The synthesis of diols based on the dimer of butadiene

It has been shown that the reaction of equimolar quantities of butadiene and epoxide with alkali metal in tetrahydrofuran results in the formation of the dimer diol on subsequent hydrolysis. Yields up to 70% have been obtained with lithium metal, but with sodium the reaction is less efficient.     

Vinyl polymerization. 201. Polymerization of methyl methacrylate initiated by diphenyldiazomethane or by methyl 1-methyl-2-(9′-anthryl)-cyclopropylcarboxylate

A study on the polymerization of methyl methacrylate (MMA) initiated by methyl 1-methyl-2-(9′-anthryl)-cyclopropylcarboxylate (ACP) and by diphenyldiazomethane (DDM) was made. It was found that ACP could polymerize MMA with almost the same rate as 9-anthryldiazomethane. The rate of the polymerization initiated by DDM was found to be expressed by the equation: Contrary to ACP, methyl 1-methyl-2.2-diphenyl-cyclopropylcarboxylate was found to be unable to initiate the polymerization of MMA at 80°C.     

Controlled Radical Polymerization of Vaporized Vinyl Monomers on Solid Surfaces under UV Irradiation

Summary: In order to prepare well‐defined polymers on solid surfaces in the gas phase, a gas phase‐assisted surface polymerization (GASP) of vinyl monomers was carried out on solid surfaces pre‐coated with a photoiniferter, 2‐cyanoprop‐2‐yl N,N′‐dimethyldithiocarbamate, under UV irradiation. The GASP of methyl methacrylate (MMA) resulted in the formation of polymer on the surfaces and showed a proportional relationship between and polymer yield. Consecutive copolymerization of MMA and styrene led to the formation of a block copolymer, which was confirmed by a selective solvent fractionation method. These results demonstrate that controlled radical polymerization of vaporized monomer occurred on the solid surfaces.

Expected mechanism of GASP under UV irradiation.     

Metal-containing initiator systems. XIII. Free radical initiation of vinyl polymerization with systems containing metallic tin or tin compounds

An investigation has been made on the polymerization of methyl methacrylate (MMA), with the following initiator systems: 1. binary system of metallic tin and benzyl chloride, 2. binary system of reduced nickel and tin tetrachloride, and 3. benzyltin compounds. All systems were found to initiate the radical polymerization of MMA. The rate of polymerization (R_p) of MMA initiated with tetrabenzyltin in benzene at 80°C may be expressed as follows: The overall activation energy for this polymerization was estimated to be 12.5 kcal/mole. Tetrabenzyltin was also observed to serve as a photosensitizer in the polymerization of MMA. It was also found that the system metallic tin/benzyl chloride induced selectively the cationic polymerization of isobutyl vinyl ether as well as the radical polymerization of MMA.     

Effect of metal ion on the radical polymerization of methyl methacrylate

The polymerization of methyl methacrylate (MMA) initiated by azoisobutyronitrile (AIBN) in the presence of various metal chlorides and water was investigated in N,N-dimethylformamide (DMF). The order of catalytic activity of the metal chlorides for the polymerization of MMA is as follows: A complex formation between poly(methyl methacrylate) (PMMA) and the metal ions was observed from the measurement of the solution viscosity of PMMA in the presence of the same metal ions in DMF.     

The dimerization of 1-alkynes by rhodium(I) catalysts. Effect of phosphorus ligands on regioselectivity

The dimerization of 1-alkynes by rhodium(I) complexes in the presence of phosphorus ligands is described. The products are linear and branched dimers, the ratio of which is correlated with the electronic parameters, v_CO of Ni(CO)₃L, of the ligands L, but no simple correlation is apparent between their steric parameter and the selectivity. Electron-donating ligands promote the formation of the linear dimer. The substituents of the 1-alkynes also affect the distribution of linear and branched dimers. Electron-donating substituents prefer linear isomer to branched one. The reactivity of the substituted 1-alkynes (R? C?C? H) increased with substituent R in the order      

Polymerization of methyl methacrylate initiated by trichloroacetyl chloride and water

A kinetic study on the polymerization of methyl methacrylate (MMA) initiated by trichloroacetyl chloride (TAC) and water was made dilatometrically. The reaction proceeds by a radical mechanism, and the initial rate of polymerization is described by the equation: The overall activation energy of the initiation was estimated as 4.8 kcal/mole. A probable initiation mechanism was proposed from the kinetic results and the liquid gas chromatographic data.     

Vinyl polymerization with dimethylaniline/cupric nitrate system

A study of vinyl polymerizations initiated with the system of dimethylaniline (DMA) and cupric [Cu(II)] nitrate has been made. This initiator system was found to induce the polymerization of vinyl monomers having an electron-attracting substituent such as methyl methacrylate (MMA) and acrylonitrile, but it does not initiate the styrene and vinyl acetate polymerizations. The rate of polymerization (R_p) of MMA with this system was expressed by the following Eqs., depending upon the Cu(II) concentration used: The apparent activation energy for this polymerization was found to be 16.5 and 14.4 kcal/mole for the above two Cu(II) concn. ranges, respectively. The polymer of MMA obtained by this system was found to contain an endgroup similar to dimethylaniline, probably a methylanilinomethyl group, from the determination of its UV spectrum.     

Crystal structure of oligourethane. III. Crystal structure of acetoxy(pentamethyleneurethane) dimer

The crystal structure of acetoxy(pentamethyleneurethane) dimer, was studied by the X-ray diffraction method. The crystal is triclinic with The diffraction patterns clearly show the existence of a subcell which is also triclinic with two (CH₂)₂ units in the unitcell. The subcell structure was determined by use of special non space group extinctions. The proposed crystal structure is that each of the two molecular chains in the main unit cell is connected side by side with other chains in the neighbouring cells by two hydrogen bonds to form molecular sheets parallel to the b_s c_s plane.     

Critically evaluated rate coefficients for free‐radical polymerization, 3. Propagation rate coefficients for alkyl methacrylates

Pulsed‐laser polymerization (PLP) in conjunction with the analysis of the molecular weight distribution (MWD) via size‐exclusion chromatography (SEC) remains recommended by the IUPAC Working Party on Modeling of polymerisation kinetics and processes as the method of choice for the determination of propagation rate coefficients, k_p, in free‐radical polymerization. k_p data from PLP‐SEC studies in several laboratories for ethyl methacrylate (EMA), butyl methacrylate (BMA) and dodecyl methacrylate (DMA) bulk free‐radical polymerizations at low conversion and ambient pressure are collected. The data fulfill consistency criteria and the agreement among the data is remarkable. These values are therefore recommended as constituting benchmark data sets for each monomer. The results are best fit by the following Arrhenius relations: For the methacrylates under investigation k_p increases with the size of the ester group. For example, in going from MMA to DMA, k_p at 50°C is enhanced by a factor of 1.5.     

Vinyl polymerization initiated by the dimethylaniline N-oxide/tosyl chloride system

A study of the vinyl polymerization initiated by the system dimethylaniline N-oxide (DMAO) in conjunction with tosyl chloride (TsCl) has been performed. According to the kinetic results of the polymerization of methyl methacrylate (MMA) and of the copolymerization of MMA with styrene, the polymerization proceeds via a radical mechanism. The rate of polymerization is given by the following equation: and the overall activation energy was calculated to be 14.3 kcal · mole^?1. According to the UV spectrum, the poly-MMA obtained probably contains N-methylanilinomethyl end groups. A graft polymer was obtained by polymerization of MMA with DMAO and partially chlorosulfonated polyethylene (Hypalon-30). From the results an initiation mechanism is proposed and discussed.     

Iron(III)‐Mediated AGET ATRP of Methyl Methacrylate Using Vitamin C Sodium Salt as a Reducing Agent

Vitamin C sodium salt (VC‐Na) is used as a reducing agent for the iron‐mediated AGET ATRP (atom transfer radical polymerization using activators generated by electron transfer) of methyl methacrylate (MMA) with FeCl₃/tris‐(3,6‐dioxa‐heptyl) amine (TDA‐1) as a catalyst complex and ethyl 2‐bromoisobutyrate (EBiB) as an initiator in the absence/presence of a limited amount of air. As compared with the reported iron‐mediated AGET ATRP of MMA, the current catalyst system shows a faster polymerization rate. For example, a conversion of 82.3% is obtained in 3.1 h with a molar ratio of [MMA]₀/[EBiB]₀/[FeCl₃.6H₂O]₀/[TDA‐1]₀/[VC‐Na]₀ = 500:1:1:3:0.5 at 90 °C. The kinetics of polymerizations of MMA in bulk or anisole demonstrate features of “living” or controlled free‐radical polymerization, such as the number‐average molecular weights increasing linearly with monomer conversion and maintaining narrow molecular weight distributions ( / = 1.20–1.44).

     

Reverse Atom Transfer Radical Polymerization of Methyl Methacrylate using a New Catalyst,Copper(II) N,N′‐Butyldithiocarbamate

Summary: The homogeneous bulk reverse ATRP using AIBN/Cu(SC(S)N(C₄H₉)₂)₂/bpy as the initiating system has been successfully carried out for methyl methacrylate. Well‐controlled polymerizations with low polydispersities ( = 1.10–1.30) have been achieved. The revised number‐average molecular weights ( 's) increased linearly with monomer conversion and were close to the values. The polymerization rate followed the first‐order kinetics in monomer, while it is about 2.0 order in initiator concentration and 1.15 order in Cu(II) concentration. The k values for the homogeneous bulk reverse ATRP of MMA initiated by AIBN/Cu(SC(S)N(C₄H₉)₂)₂/bpy (1:2:6) at 80, 90, 100 and 110 °C were 0.402 × 10^?4, 1.021 × 10^?4, 2.952 × 10^?4, and 3.687 × 10^?4 (s^?1), respectively. On the basis of the Arrhenius plot, the apparent activation energy was calculated to be ΔE = 87.1 kJ/mol. The obtained PMMA was functionalized with an ultraviolet light sensitive ω‐SC(S)N(C₄H₉)₂ group characterized by means of ¹H NMR spectroscopy, and which was also proved by its chain extension with fresh MMA under UV‐light irradiation at room temperature. A polymerization mechanism for this novel initiation system is proposed.

Dependence of and on the monomer conversion for the homogeneous bulk reverse ATRP of MMA at different concentration of catalyst.     

Thermally Induced Aerobic Autopolymerization of Methyl Methacrylate in Amide‐Type Solvents: Simultaneous Polymerization during Induction via Direct In Situ O2 Activation

The thermally induced spontaneously initiated autopolymerization of methyl methacrylate (MMA) upon air exposure in amide‐type polar solvents at 75–90 °C is unexpectedly observed and then investigated. By using iodometric analysis, it is confirmed that oligo(MMA peroxide)s in situ form at a moderate rate via thermally induced interpolymerization of MMA with O₂ diffusing from air above 70 °C and give rise to an equivalent concentration above 10^?4 mol L^?1 in 2–4 h in N,N‐dimethylacetamide, N,N‐dimethylformamide, and N‐methyl‐2‐pyrrolidinone (in a descending order of the formation rate). Simultaneously, oligo(MMA peroxide) undergoes thermally induced homolytic decomposition into alkyloxyl radicals to initiate polymerization of MMA in the above solvents at a rate comparable to those initiated by chemical initiators. Thus, the thermally induced in situ O₂ activation into peroxides via interpolymerization accounts for the spontaneous initiation of the autopolymerization of MMA in these solvents at moderate temperature.

     

ATRP of Allyl Methacrylate with Alkyl Methacrylates – Crosslinking of Poly(methacrylate)s with Allyl Ester Side Groups

Summary: Random copolymers of methyl methacrylate (MMA), butyl methacrylate (BMA) and allyl methacrylate (AMA) were prepared via atom transfer radical polymerization (ATRP). AMA is a bifunctional monomer with two double bonds of different reactivity: a highly reactive methacrylate double bond and an allyl ester double bond of lower reactivity. In order to obtain linear polymers with pendant allyl ester groups, the copolymerization conditions have to be optimized with respect to the concentration of AMA, the catalyst system applied – especially the ligand – and the temperature. By means of kinetic studies the reaction parameters for a controlled polymerization were determined. The results obtained show that the higher the temperature and the amount of AMA is the higher is the probability of irregular chain growth and side reactions induced by the pendant allyl ester groups such as hydrogen abstraction from the allyl position or radical addition to the allyl ester double bond. The random copolymers were photochemically crosslinked by using 2,2‐dimethoxy‐2‐phenylacetophenone as photoinitiator. The thermal properties of linear and crosslinked polymers were determined. The glass transition temperatures of both show no significant difference at low AMA content and thus low crosslinking densities.

GPC eluograms of MMA/BMA (70:30) copolymers with 5 mol‐% AMA at different conversions.     

Determination of Homopolymerization Kinetics of 10‐(N‐Methylacrylamido)‐decylphosphonic acid,Its Diethyl ester,and 10‐(Methacryloyloxy)‐decylphosphonic acid,and Their Copolymerization with Methyl methacrylate

Two polymerizable phosphonic acids destined to be constituents of self‐etch adhesives as well as a diethyl phosphonate bearing an N‐methylacrylamide group are examined for their polymerization and copolymerization activity in methanol between 45 and 65 °C. Polymerization proceeds readily through a thermal free radical initiator. The intensity exponents for the monomer and initiator are only slightly over 1 and ≈0.5, respectively, in accordance with the results typically observed for an ideal free radical polymerization with bimolecular termination. The specific feature of this process is the absence of auto‐acceleration during the phosphonic acid monomer polymerization and polymer network formation in case of the phosphonate monomer. The kinetics of copolymerization with methyl methacrylate (MMA) are monitored by online ¹H NMR spectroscopy. Two copolymerization reactions for each pair of comonomers are sufficient to evaluate the kinetic data using the Jaacks method, the Fineman–Ross method, and the nonlinear least squares method. All three methods give similar results for particular monomer/MMA couples.

     

A Highly Efficient Iron‐Mediated AGET ATRP of Methyl Methacrylate Using Fe(0) Powder as the Reducing Agent

A new method, AGET ATRP mediated by an iron(III) catalyst using Fe(0) powder as a reducing agent and MMA as a model monomer, is reported. The polymerizations can be carried out in the absence or presence of a limited amount of air and show the features of a “living”/controlled radical polymerization. MMA conversions of 90.3 and 80.0% can be obtained in 3.5 and 4.0 h in the absence/presence of a limited amount of air, respectively, for the iron‐mediated AGET ATRP with a molar ratio of [MMA]₀/[EBiB]₀/[FeCl₃ · 6H₂O]₀/[PPh₃]₀/[Fe(0)]₀ = 600:1:0.5:2:0.1 at 90 °C. PMMA with molecular weights of 55 060 and 47 790 g · mol^?1 and with molar‐mass dispersity of 1.24 and 1.28, respectively, can be obtained correspondingly.

     

Diblock Copolymers Based on 1,4‐Dioxan‐2‐one and ε‐Caprolactone: Characterization and Thermal Properties

Summary: Various poly(ε‐caprolactone‐block‐1,4‐dioxan‐2‐one) (P(CL‐block‐PDX)) block copolymers were prepared according to the living/controlled ring‐opening polymerization (ROP) of 1,4‐dioxan‐2‐one (PDX) as initiated by in situ generated ω‐aluminium alkoxides poly(ε‐caprolactone) (PCL) chains in toluene at 25 °C. 1 ¹H NMR, PCS and TEM measurements have attested for the formation of colloids attributed to a growing PPDX core surrounded by a solvating PCL shell during the polymerization of PDX promoted by ω‐Al alkoxide PCL chains in toluene. The thermal behavior of the P(CL‐block‐PDX) copolymers was studied by DSC; showing two distinct melting temperatures (as well as two glass transition temperatures) similar to those of the respective homopolyesters. Finally, the thermal degradation of the P(CL‐block‐PDX) block copolymers was investigated by TGA simultaneously coupled to a FT‐IR spectrometer and a mass spectrometer for evolved gas analysis (EGA). The degradation occurred in two consecutive steps involving a first unzipping depolymerization of the PPDX blocks followed by the degradation of the PCL blocks via both ester pyrolysis and unzipping reactions.

TEM observation of P(CL‐block‐PDX) block copolyesters ( = 11 600 and = 22 100) as formed by vaporization starting from a diluted suspension in toluene/TCE mixture solvent (50/50 v/v).     

Synthesis and Characterization of Poly(trimethylene oxide)‐block‐Polystyrene and Poly(trimethylene oxide)‐block‐Polystyrene‐block‐Poly(methyl methacrylate) by Combination of Atom Transfer Radical Polymerization (ATRP) and Cationic Ring‐Opening Polymerization (CROP)

Summary: Diblock copolymers, poly(trimethylene oxide)‐block‐poly(styrene)s abbreviated as poly(TMO)‐block‐poly(St), and triblock copolymers, poly(TMO)‐block‐poly(St)‐block‐poly(MMA)s (MMA = methyl methacrylate), with controlled molecular weight and narrow polydispersity have been successively synthesized by a combination of atom transfer radical polymerization (ATRP) and cationic ring‐opening polymerization using the bifunctional initiator, 2‐hydroxylethyl α‐bromoisobutyrate, without intermediate function transformation. The gel permeation chromatography (GPC) and NMR analyses confirmed the structures of di‐ and triblock copolymers obtained.

GPC curves of (a) poly(St); (b) diblock copolymer, poly(St)‐block‐poly(MMA) before precipitation; (c) poly(St)‐block‐poly(MMA) after precipitation in cyclohexane/ethanol (2:1); (d) triblock copolymer, poly(TMO)‐block‐poly(St)‐block‐poly(MMA).