Aqueous polymerization of acrylic acid initiated by KMnO4 — H2C2O4 redox system

Polymerization of acrylic acid in aqueous solution initiated by permanganate-oxalic acid redox pair has been studied at 32 ± 0.2°C in nitrogen atmosphere. The rate of polymerization has been found to be nearly independent of oxalic acid concentration within the range 1.87 to 9.33 · 10^?3 mole/l. and decreases only at higher concentrations of the oxalic acid. The rate has also been found to vary with the first power of the monomer concentration (within the range 1.44 to 5.76 · 10^?2 mole/l.) and the first power of the catalyst concentration (8.0 to 28.0 · 10^?5 Mole/l.). It is, however, proportional to half power at relatively high catalyst concentration, at fixed concentrations of oxalic acid (1.03 · 10^?2 mole/l.) and the monomer (5.76 · 10^?2 mole/l.). At higher concentration of monomer the catalyst exponent has been found to be nearly unity for both the higher and lower concentrations of the catalyst. The initial rate of polymerization increases with increase in temperature. The overall energy of activation has been found to be 19.56 kcal/mole within the temperature range 30 – 45°C. Organic solvents and salts (KCI, Na₂SO₄, and Na₂C₂O₄) depress the rate but MnSO₄ 4H₂O has been found to increase the initial rate but depress the maximum conversion.     

Aqueous polymerization of methacrylic acid initiated by permanganate/oxalic acid redox system

The polymerization of methacrylic acid initiated by permanganate / oxalic acid redox pair has been studied in aqueous media at 30 ± 0.2°C in nitrogen atmosphere. The initial rate of polymerization has been found to be proportional to nearly the first power of the catalyst (KMnO₄) concentration ((0.8-6.0)·10^?4 mole/l.) at low monomer concentration (5.89·10^?2 mole/l.) but the catalyst exponent varies from 1.2 to 0.2 at comparatively high monomer concentration (17.68·10^?2 mole/l.) and falls at comparatively higher concentrations of the activator ((COOH)₂) at constant concentration of catalyst (1.6·10^?4 mole/l.) and monomer (5.89·10^?2 mole/l.). The rate is proportional to the first power of the monomer concentration within the range (2.36–14.1)·10^?2 mole/l. and catalyst (2.8·10^?4 mole/l.). The initial rate increases with increase in polymerization temperature up to 45°C. The overall activation energy has been found to be 9.87 kcal/mole within the temperature range 30-45°C. Organic solvents (water miscible only) and salts (KCl, Na₂SO₄ and Na₂C₂O₄) depress the rate considerably but the manganous salt (MnSO₄) is found to increase the initial rate. A complexing agent, NaF, decreases the rate as well as the maximum conversion. Introduction of new catalyst at intermediate stages of polymerization increases the rate and the maximum conversion.     

Aqueous polymerization of methacrylamide initiated by the redox system K2S2O8/ascorbic acid

The polymerization of methacrylamide initiated by the redox system K₂S₂O₈/ascorbic acid has been studied at 35 ± 0,2°C under the influence of atmospheric oxygen. The molecular oxygen autocatalyses the polymerization rate. The rate of polymerization is independent of the activator (ascorbic acid) concentration within the range 2,83 · 10^?3 to 11,3 · 10^?3 mol · l^?1, this does not hold below or above the given concentration range. The rate varies linearly at low monomer concentration (up to 17,76 · 10^?2 mol · l^?1). The catalyst exponent decreases from nearly unity (0,94) to 0,57 with increasing concentration of the catalyst probably due to participation of primary radicals in the termination of growing chain. The initial rate is not changed by the addition of a strong acid (H₂SO₄) within the range 15 · 10^?5 to 30 · 10^?5 mol · l^?1. With the activator (ascorbic acid) alone, an optimum is observed within the pH range 2,9–3,5. The initial rate and the limiting conversion increases with increasing polymerization temperature. The overall energy of activation as calculated from the ARRHENIUS plot has been found to be 16,0 kcal.mol^?1 within the temperature range 30–45°C. Organic solvents (water miscible only) and small amounts of neutral salts, (KCl, Na₂SO₄) depress the initial rate and the maximum conversion. The addition of small amounts of catalysts like Cu^2⊕, Mn^2⊕, Ag^oplus; increases the initial rate but no appreciable increase in the limiting conversion is observed.     

Aqueous polymerization of acrylamide initiated by acidic thiourea/potassium bromate redox system

The aqueous polymerization of acrylamide initiated by bromate/thiourea redox system has been studied in acidic media at 25 ± 0.2°C in a nitrogen atmosphere. The rate of polymerization has been found to vary with the first power of the potassium bromate concentration within the range 0.75·10^?2 to 2.0·10^?2 mole·1^?1 and nearly with the first power of the hydrochloric acid concentration within the range 2.85·10^?2 to 8.55·10^?2 mole·1^?1. However, the rate of polymerization is independent of the thiourea concentration, but varies with the first power of the monomer concentration within the range 6.0·10^?2 to 10.0·10^?2 mole·1^?1. The initial rate increases but the maximum conversion decreases as the temperature increases within the range 19 to 35°C. The over all energy of activation has been found to be 22.9 kcal·mole^?1 within the temperature range mentioned above. Water miscible organic solvents and mono- and dibasic salts show the same effect as given by MISRA et al. The effect of cationic and anionic surfactants has been found to increase and decrease the rate of polymerization (R_p) respectively, however non-ionic detergents have no effect on the (R_p).     

Studies on aqueous polymerization of acrylamide, 4. Potassium persulfate/thioglycolic acid redox system

Aqueous polymerization of acrylamide, initiated by the potassium persulfate-thioglycolic acid redox pair, was studied at 30°C under introgen. The initial rate of polymerization R was found to be approximately proportional to the 0,5th power of potassium persulfate concentration within the range of 0,6 to 1,0 mmol^?1. R was also found to vary linearly with the monomer concentration between 0,8 · 10^?1 and 1,0·10^?1 mol l^?1 and to increase with the thioglycolic acid concentration in the interval of 3,0 to 4,0 mmol l^?1. The activation energy was estimated to be 126 kJ mol^?1. Addition ot NaCl, NaF, and (CH₃)₄NI lowered the initial rate R while MnSO₄ increased it. Some aliphatic alcohols were observed to be polymerization retarders.     

Aqueous redox polymerization of acrylamide initiated by citric acid/permanganate

The homogeneous redox polymerization of acrylamide by the citric acid/permanganate initiating system was investigated at 35±0,2°C under nitrogen. Variation of the activator concentration in the range of 2,5.10^?3 to 20,0.10^?3 mol/dm³ had no effect on the rate of polymerization. The initial rate increased with the increasing catalyst concentration and a value of nearly unity of the catalyst exponent confirmed a unimolecular chain termination process. The rate varied linearly with the monomer concentration over a wide range (5,0.10^?2 to 20,0.10^?2mol/dm³). The initial rate increased with the increasing temperature but the maximum conversion showed a decrease as the temperature was raised above 35°C. The energy of activation, in the temperature range of 25 to 45°C, was found to be 55,90kJ/mol (13,36 kcal/mol). The addition of neutral salts, Co(NO₃)₂, Ni(NO₃)₂, organic solvents, and complexing agents, all water soluble, reduced the rate and percentage of conversion. The introduction of MnSO₄ or of more catalyst (at intermediate stages) into the system increased both the rate and limiting conversion.     

Studies on aqueous polymerization of acrylamide, 2. Potassium persulfate/2-mercaptoethanol redox system

The polymerization of acrylamide in aqueous media initiated by the potassium persulfate/2-mercaptoethanol redox pair was studied at 30°C under nitrogen atmosphere. The initial rate of polymerization was found to be proportional to nearly the 1,5th power of the potassium persulfate concentration within the range of 0,6 to 2,0 mmol l^?1 and to the first power of acrylamide concentration in the range of 0,1 to 0,14 mol l^?1. The rate was also found to be proportional to the first power of the 2-mercaptoethanol concentration within the range 4,0 to 8,0 mmol l^?1. The overall activation energy was found to be 134 kJ mol^?1. Further the effect of salts (NaCl, KCl, NH₄Cl, Na₂C₂O₄, K₂C₂O₄·H₂O, (NH₄)₂C₂O₄,MnSO₄·4H₂O, and NaF) and aliphatic alcohols (methanol, ethanol, and propanol) was tested.     

Functionalized monomers, 2. Kinetics of radical polymerization of oxirane- and oxetane-derivatives of styrene and copolymerization of 4-vinylphenyloxirane with styrene

The kinetics of radical polymerization of 4-vinylphenyloxirane ( 1 ), 4-vinylbenzyloxirane ( 2 ), and 2-(4-vinylphenyl)oxetane ( 3 ) initiated by 2,2′-azoisobutyronitrile (AIBN) was studied. In the case of 1 the initial rate of polymerization was found to depend on the initiator and monomer concentrations as (r_p)_total ∝? [AIBN]^0,5 · [M₁]^1,36. The higher order of the polymerization rate with respect to 1 was interpreted as due to a concurrent thermally initiated polymerization; the rate of the latter was found to depend on the monomer concentration squared. The value of the ratio propagation rate constant over square root of termination rate constant k_p/k_t^1/2 = 2,8 · 10^?2 dm^3/2 · mol^?1/2 · s^?1/2 was determined from the measured dependences (r_p)_total = f[AIBN] and (r_p)_total = f([M₁]), corrected for the rate of thermally initiated polymerization of 1 . On the other hand, the kinetics of radical polymerization of 2 and 3 did not deviate from the standard scheme valid for radical polymerization; in both cases the observed reaction order with respect to initiator and monomer was 0,5 and 1, respectively. Radical copolymerization of 4-vinylphenyloxirane (M₁) with styrene (M₂) was characterized by monomer reactivity ratios r₁ = 1,06 and r₂ = 0,78, respectively, corresponding to the Q, e-scheme values Q = 0,9 and e = ?0,36 for monomer 1 .     

Aqueous polymerization of acrylamide initiated by acidic permanganate/thiourea redox system

The polymerization of acrylamide, initiated by acidic permanganate/thiourea redox system, was studied in aqueous media at 30 ± 0,2 °C in nitrogen. The rate of polymerization (R_p) was found to be proportional to nearly the first power of the catalyst (KMnO₄) concentration, within the range of 0,5 · 10^?2 to 1,4 · 10^?2 mol dm^?3, and independent of the thiourea concentration. However, the rate of polymerization varies with the first power of the hydrochloric acid concentration within the range of 2,85 · 10^?2 to 11,4 · 10^?2 mol dm^?3, and increases linearly up to certain extent by varying the monomer concentration from 2,5 · 10^?2 to 12,5 · 10^?2 mol dm^?3. A deviation from the linear behaviour is observed, however, above a concentration of 12,5 · 10^?2 mol dm^?3. The initial rate of polymerization (R_i) as well as the maximum conversion increases by increasing the temperature up to 35 °C, but the maximum conversion falls as the temperature rises above 35 °C. The overall energy of activation is found to be 47,70 kJ mol^?1 (11,48 kcal/mol^?1) within the temperature range of 25–45 °C. Addition of salts, except manganous salts, was found to be associated with a depression in the R_p and maximum conversion. The effect of cationic and anionic surfactants has been found to increase and decrease the R_p respectively; non-ionic detergents, however, have no effect on the R_p.     

Permanganate-malic acid redox pair as the initiating system in the homogeneous polymerization of acrylamide

The homogeneous polymerization of acrylamide initiated by the new redox system permanganate-malic acid was investigated in aqueous media under nitrogen at 35±0,2°C. Over a wide range of concentration (2,5 to 30 mmol dm^?3) of the activator (malic acid), ( 4 ), the polymerization rate remains unaffected. Addition of sulfuric acid (0,1 to 5 mmol dm^?3) increases the rate but decreases the maximum conversion. The value 0,53 of the catalyst exponent confirms a bimolecular termination mechanism. The variation of the rate at a low monomer concentration is linear. The initial rate and the conversion increase with increasing temperature. The activation energy is found to be 82,20 kJ/mol (19,74 kcal/mol) in the temperature range of 25 to 50°C. Neutral salts, water miscible organic solvents, and ethylenediaminetetraacetic acid all suppress both the limiting conversion and the rate of polymerization. The addition of more catalyst at intermediate stages as well as the addition of MnSO⁴ raise the initial rate and the conversion. Sodium fluoride enhances the rate but lowers the limiting conversion.     

Effect of SnCl4 on the radical-initiated polymerization of diethyl itaconate: Kinetical and ESR studies

The effect of SnCl₄ on the polymerization of diethyl itaconate ( 1 ) with dimethyl 2,2′-azoisobutyrate ( 2 ) in benzene was investigated kinetically and ESR spectroscopically. The polymerization rate (R_p) at 50°C shows a flat maximum on varying the SnCl₄ concentration. The molecular weight of the resulting polymer decreases with increasing SnCl₄ concentration. The overall activation energy of the polymerization is lowered from 52 to 33 kJ · mol^?1 by the presence of SnCl₄, (0,342 mol · L^?1). An NMR study revealed that 1 and SnCl₄ form 1:1 and 2:1 complexes with a large stability constant in benzene. The propagating polymer radicals in the absence and presence of SnCl₄ are ESR-observable as a five-line spectrum under the actual polymerization conditions. The complexed polymer radicals show further three-line splitting due to two methylene hydrogens of the ethyl ester group. The polymer radical concentration increases with the SnCl₄ concentration. The rate constant (k_p) of propagation was determined using R_p and the polymer radical concentration. k_p (6,3–2,9 L · mol^?1 · s^?1 at 50°C) decreases with increasing SnCl₄ concentration. The presence of SnCl₄ (0,342 mol · L^?1) reduces the activation energy of propagation from 29 to 21 kJ · mol^?1. The rate constant (k_t) of termination was estimated from the decay curve of the polymer radicals, k_t (3,1–1,1 · 10⁵ L · mol^?1 s^?1) also decreases with the SnCl₄ concentration. The activation energies of termination in the absence and presence of SnCl₄ (0,342 mol · L^?1) are 30 and 24 kJ · mol^?1, respectively. Suppression of propagation and termination by SnCl₄ seems to be explicable in terms of an entropy factor.     

Kinetics of the nitrogen dioxide initiated polymerization of acrylic acid

Acrylic acid (AA) was polymerized with NO₂ in tetrahydrofuran (THF) and in 1,4-dioxane. The effects of monomer and initiator concentration and of temperature on polymer conversion, initial rate of polymerization, and molecular weight were studied. The overall activation energy of polymerization was found to be 16,3 kcal mol^?1 (68,23 kJ · mol^?1) and 15,54 kcal · mol^?1 (65,05 kJ · mol^?1) in THF and in 1,4-dioxane, respectively. High molecular weight polymers (M ca. 10⁵) were obtained. The polymerization appears to be initiated by free radicals.     

Studies on aqueous polymerization of acrylamide. Potassium persulfate/2-mercaptoethylamine hydrochloride redox system

The kinetics of aqueous polymerization of acrylamide, initiated by the potassium persulfate(K₂S₂O₈)/2-mercaptoethylamine hydrochloride (MEAH) redox pair was studied under nitrogen atmosphere at 30 ± 0,1 °C. The initial rates of polymerization were found to be proportional to [K₂S₂O₈]^1,5 (in the range of 0,8 to 1,2 mmol^?1), to [acrylamide]¹ (in the range of 0,8.10^?1 to 1,2.10^?1 mol 1^?1), and to [MEAH]¹ (in the range of 1,0 to 7,0mmol 1^?1), respectively. The overall energy of activation was found to be 9,8 kcal mol^?1 (40kJ mol^?1). Water miscible alcohols and common salts (NaF, NaCl, (CH₃)₄NI) appeared to depress both the polymerization rate and the maximum conversion. With MnSO₄.4H₂O the reverse influence was found.     

Propylene polymerization on titanium-magnesium catalysts determination of the number of active centers and propagation rate constants

By use of the quenching technique with ¹⁴CO and ¹⁴CO₂ the number of active centers and the propagation rate constants (k_p) were determined for the propylene polymerization on different titanium-magnesium catalysts in the presence and absence of an organoaluminium cocatalyst. The k_p values at 70°C were found to be 500–1000 1·mol^?1·s^?1, which were confirmed by independent data of molecular mass measurements of the isotatic polymer after a short polymerization time (5 s). Similar isotactic and atactic k_pvalues were found. The maximum number of active centers for supported titanium-magnesium catalysts can reach about 10% of the titanium content in the catalyst. The k_p values of ethylene polymerization on catalysts active without an organoaluminium cocatalyst were also determined (≈ 10⁴ l·mol^?1·s^?1 at 70°C).     

Solvent effect on the propagation rate constant in the radical polymerization of bis(2-ethylhexyl) itaconate

Polymerization of bis(2-ethylhexyl) itaconate ( 1 ) with dimethyl azobis(isobutyrate) ( 2 ) was carried out at 50°C in various solvents. Polar solvents caused a significant decrease in the polymerization rate (R_p) and the molecular weight of resulting poly( 1 ). The propagating poly( 1 ) radical could be observed as a five-line ESR spectrum in the actual polymerization systems used. The stationary concentration of poly( 1 ) radical was determined by ESR to be 4,2–6,4 · 10^?6 mol · L^?1 at 50°C when the concentrations of 1 and 2 were 1,03 and 3,00 · 10^?2 mol · L^?1. Using R_p the monomer concentration and the polymer radical concentration, the propagation rate constant (K_p) was estimated to be 1,4–6,8 L · mol^?1 · s^?1, depending on the solvents used. The k_p value was smaller in more polar solvents. The solvent effect is explained in terms of the solvent affinity for the propagating polymer chain.     

Studies on the aqueous polymerization of acrylamide by the acidified potassium permanganate-thioglycolic acid redox system

The polymerization of acrylamide in aqueous media, initiated by the acidified potassium permanganate/thioglycolic acid ( 1 ) redox pair was studied at 30±0,1°C in an inert atmosphere of dry and oxygen-free nitrogen. The initial rate of polymerization was found to be proportional to nearly the first power of potassium permanganate concentration within the range of 2,0.10^?3 to 6,0.10^?3 moll^?1. The rate was also found to be proportional to the first power of [acrylamide] in the range of 8,0.10^?2 to 10,0.10^?2 moll^?1. The rate of polymerization appears to be independent of thioglycolic acid ( 1 ) concentration in the range of 1,0.10^?2 to 1,2.10^?2moll^?1. At still higher concentrations, however, the amount of 1 depresses the rate and maximum conversion. An excess of sulphuric acid was found to affect the rate of polymerization to a slight extent and a deficiency of the acid makes the reaction to stop at an early stage, during the range studied. This indicates, therefore, the presence of an optimum concentration of H₂SO₄ for the smooth initiation of polymerization. A study on the effect of salts reveals that KCl and NH₄Cl lower the initial rate of polymerization, whereas the reverse is true for MnSO₄.H₂O and Na₂C₂O₄. The water-miscible aliphatic alcohols e.g. CH₃OH, C₂H₅OH, (CH₃)₂CHOH, and C₄H₉OH were found to depress the extent of polymerization.     

The initiation of polymerization of unsaturated tertiary amines with carboxylic acids

The polymerization rate (R_p) of N-methyl-N-phenyl-2-aminoethyl methacrylate (MPAEMA) initiated with 2,2' -azodiisobutyronitrile (AIBN) at 50°C increased considerably after the addition of CCI₃COOH, and distinctly after the addition of CH₃COOH. R_p in a benzene solution of 2 mol. dm^?3 MPAEMA and 5 · 10^?2 mol. dm^?3 CCl₃COOH (without AIBN) was 13% · h^?1. [η] of the obtained polymer corresponded to 64 cm³ · g^?1. The polymerization order of MPAEMA initiated with CCl₃COOH is 0,93 with respect to monomer and 0,51 with respect to CCl₃COOH. The overall activation energy of polymerization of MPAEMA calculated from the temperature dependence of R_p between 20 and 50°C is 43 ± 1,2 kJ · mol^?1. In a benzene solution of 2 mol.dm^?3 MPAEMA, 5 · 10^?2 mol · dm^?3CCl₃COOH and 5 · 10^?3 mol · dm^?3 1,4-benzoquinone at 50°C the polymerization does not proceed for 6 h. In a benzene solution of 2 mol · dm^?3 4-dimethylaminostyrene (4-DMAS) and 2 mol · dm^?3 CH₃COOH (without AIBN), 40% of monomer polymerized within one hour. [η] of the polymer was 4 cm³ · g^?1. The overall activation energy of polymerization of 4-DMAS in the presence of CH₃COOH is ca · 54 kJ · mol^?1. The addition of 5 · 10^?3 1,4-benzoquinone slows down the polymerization rate only slightly. The effect of acids on the elementary polymerization reactions is characterized.     

Kinetic and ESR studies on radical polymerization. Radical polymerization behavior of N-octadecylmaleimide in benzene

The polymerization of N-octadecylmaleimide ( 1 ) initiated with azodiisobutyronitrile ( 2 ) was investigated kinetically in benzene. The overall activation energy of the polymerization was calculated to be 94,2 kJ·mol^?1. The polymerization rate (R_p) at 50°C is expressed by the equation, R_p = k[ 2 ]^0,6[ 1 ]^1,7. The homogeneous polymerization system involves ESR-detectable propagating polymer radicals. Using R_p and the polymer radical concentration determined by ESR, the rate constants of propagation (k_p) and termination (k_t) were evaluated at 50°C. k_p (33 L · mol^?1 · s^?1 on the average) is substantially independent of the monomer concentration. On the other hand, k_t (0,3 · 10⁴ – 1,0 · 10⁴ L · mol^?1 · s^?1) is fairly dependent on the monomer concentration, which is ascribable to a high dependence of k_t on the chain length of rigid poly( 1 ). This is the predominant factor for the high order with respect to the monomer concentration in the rate equation. In the copolymerization of 1 (M₁) and St (M₂) with 2 in benzene at 50°C, the following copolymerization parameters were obtained: r₁ = 0,11, r₂ = 0,09, Q₁ = 2,1, and e₁ = +1,4.     

Polymerization of 2,2-dimethyltrimethylene carbonate with tri-sec-butoxyaluminium; a kinetic study

The polymerization of 2,2-dimethyltrimethylene carbonate (DTC, 1 ) with tri-sec-butoxyaluminium (Al(O-sec-Bu)₃) proceeds with suppression of macrocyclics formation. The propagation of the polymerization proceeds pseudoanionically via insertion. Within the scope of a kinetic treatment, the time-conversion relationship was determined for the polymerization of DTC with Al(O-sec-Bu)₃ as initiator and toluene as solvent. For a polymerization temperature between 15°C and 74°C, the apparent rate constant was found to be between 0,1 and 1,0 L · mol^?1 · s^?1. Using the Arrhenius plot the experimental temperature coefficient (20,6 kJ · mol^?1) as well as the frequency factor of the polymerization (1,3 · 10³ L · mol^?1 · s^?1) were determined. Investigation of the dependence of the rate of polymerization on the initiator concentration revealed a degree of aggregation of 2 for the active species.     

Kinetic and ESR studies of the radical-initiated polymerization of N-(2,6-dimethylphenyl)itaconimide

The polymerization of N-(2,6-dimethylphenyl)itaconimide (1) with azoisobutyronitrile (2) was studied in tetrahydrofuran (THF) kinetically and spectroscopically with the electron spin resonance (ESR) method. The polymerization rate (R_p) at 50°C is given by the equation: R_p = K [2] ^0,5 · [1] ^2,1. The overall activation energy of the polymerization was calculated to be 91 kJ/mol. The number-average molecular weight of poly (1) was in the range of 3500–6500. From an ESR study, the polymerization system was found to involve ESR-observable propagating polymer radicals of 1 under the actual polymerization conditions. Using the polymer radical concentration, the rate constants of propagation (k_p) and termination (k_t) were determined at 50°C. k_p (24–27 L · mol^?1 · s^?1) is almost independent of monomer concentration. On the other hand, k_t (3,8 · 10⁴–2,0 · 10⁵ L · mol^?1 · s^?1) increases with decreasing monomer concentration, which seems mainly responsible for the high dependence of R_p on monomer concentration. Thermogravimetric results showed that thermal degradation of poly (1) occurs rapidly at temperatures higher than 360°C and the residue at 500°C was 12% of the initial polymer. For the copolymerization of 1 (M₁) with styrene (M₂) at 50°C in THF the following copolymerization parameters were found; r₁ = 0,29, r₂ = 0,08, Q₁ = 2,6, and e₁ = +1,1.