Determination of initiator decomposition constant in a heterogeneous polymerisation system

A new method for determination of initiator decomposition constant k_d is described based on the use of instantaneous polymerisation rates for two similar experiments run with different initiator concentrations. The constant found will be specific for the polymerisation system used. If the propagation and termination rate constants for the monomer are known from other studies the initiator efficiency factor f can then be obtained. To verify the validity of the method, poly(vinyl chloride) latexes were prepared by potassium persulphate (K₂S₂O₈) initiated polymerisation of submicron-sized monomer droplets. The monomer droplets were obtained by diffusion of vinyl chloride monomer into a preformed emulsion of water-insoluble oil droplets. The polymerisation was performed in an isothermal calorimeter. From the measured heat evolution, the instantaneous polymerisation rates were calculated. The thermal decomposition constant of potassium persulphate k_d was determined to be 2·5×10^-6s^-1 at 51°C. In the same system the order of reaction with respect to the initiator concentration was found to be 0·50. © 1998 SCI.     

Synthesis,characterization and kinetics of terpolymerization of acrylonitrile,N-vinyl pyrrolidone and styrene

Synthesis of a series of novel terpolymers, consisting of two electron-donating monomers, viz. N-vinyl pyrrolidone (N-VP) (heterocyclic polar monomer) and styrene (Sty) (non-polar monomer), with one electron-accepting polar monomer, i.e. acrylonitrile (AN), using α,α'-azobisisobutyronitrile as radical initiator and benzene as diluent at 60°C, has been extensively surveyed. Besides the synthesis, an attempt has been made to study the kinetics and various properties of the terpolymers, such as softening temperature and chemical resistance. The system follows non-ideal kinetics and the kinetic equation for the present system can be written as This non-ideality can be explained on the basis of significant initiator-dependent termination through primary radicals and degradative chain transfer to acrylonitrile monomer. The overall energy of activation is 72.4 kJ mol^?1 and k_p²/k_t is 0.26 × 10^?3 litre mol^?1 s^?1. The effects of various additives such as imidazolium-p-chlorophenacylide (ICPY) and ZnCl₂ were also studied. ICPY functions as a chain transfer agent (C^tr = 0.43 × 10^?4), whereas ZnCl₂ accelerates the rate of reaction. IR spectroscopy was used to confirm the structure of the terpolymers.     

Kinetics and mechanism of the thermal decomposition of potassium persulphate ions in aqueous solutions at 50°C in the presence of nitrogen gas and methacrylonitrile monomer

The initial rate of persulphate (I) decomposition at 50°C in the presence of nitrogen and methacrylonitrile (MAN) in an unbuffered aqueous solution (pH 4–7) may be written as: in the concentration ranges of persulphate (I) (0.25–2.50) × 10^?2 (m/dm³) and of (MAN) 0.18–0.36 (m/dm³). During the reaction, a white substance (polymethacrylonitrile) separates out in the colloidal state or in the precipitate form from the medium depending on the ionic strength of the medium. The pH of the medium was found to decrease rapidly and continuously with time in the absence of methacrylonitrile, but it decreased slowly and continuously with time in the presence of the monomer, MAN. If an additional quantity of MAN is injected late in a run, the rate of persulphate decomposition is further accelerated in a given run. However, the rate of persulphate decomposition is found to decrease continuously in the presence of MAN with time, i.e., as the monomer is converted to polymer. It is suggested that MAN accelerates the decomposition of persulphate ions, due to the following reactions in the aqueous phase: and where (M_j^˙)w is a-water soluble oligomeric or polymeric (j = 1–10) free radical. The estimated values of k₅ and k₁₀ are 1.05 × 10^?5 and 1.14 × 10³ (in dm³/m/s), respectively.     

Mechanism of persulfate decomposition in aqueous solution at 50°C in the presence of vinyl acetate and nitrogen

The rate of the thermal decomposition of potassium persulfate has been studied in an unbuffered aqueous solution at 50°C in nitrogen atmosphere in the presence of vinyl acetate (VA) monomer (M). It has been found that the initial rate of persulfate decomposition may be written as in the concentration range of persulfate (1.85 × 10^?2–1.85 × 10^?3 m/dm³) and VA (0.054–0.27 m/dm³). The pH of the aqueous solution of persulfate was found to decrease continuously at 50°C, but there was no measurable change of pH of the aqueous solution containing persulfate and VA at 50°C in the presence of nitrogen at the early stages of the reaction. VA, methyl acetate, and ethyl acetate have been found to undergo very slow hydrolysis in aqueous solution at 50°C. The partition coefficient (β) of the monomer between the polymer phase and the aqueous phase was found to be 21 ± 2 in the presence and absence of electrolytes (K₂SO₄, 10^?4–10^?3 m/dm³) by the bromometric estimation of the monomer present in the aqueous phase containing known amounts of monomer [1.80–2.20%, w/v] and freshly prepared polymer (0.3–0.5 g/100 mL). Above 10^?2 (m/dm³) persulfate, the polymer obtained was found to be insoluble in common solvents, viz., acetone, benzene, etc. Highly purified sodium dodecyl sulfate (0.5–5.0 × 10^?3 m/dm³) had no measurable effect on the rate of persulfate decomposition.     

Aspects of the kinetics of the radiation-induced polymerization of acrylonitrile in dimethylformamide

The radiation-induced homopolymerization of acrylonitrile (AN) in dimethylformamide (DMF) has been followed in detail over a range of monomer concentrations. In all cases a short induction period was observed which was equivalent to 1.6 × 10⁴ rad. The initial rates of polymerization for solutions of AN in DMF of mole fraction (×) of 0.33, 0.20, and 0.10 are 1.44 × 10^?5, 7.23 × 10^?6, and 2.79 × 10^?6 mole/dm³rad, respectively. Deviations of the polymerization pathway from the standard unity in monomer dependence are examined in terms of radical production ratios to the monomer and the solvent (Φ_M/Φ_S) and the polymer together with the solvent (Φ_p/Φ_s), for various mole fractions of AN in DMF. Thus, an indirect route to G_radical(events) is provided together with the corresponding k/k_t values.     

One‐pot synthesis of a polysaccharide‐based graft copolymer with an efficient redox pair (Fe2+/BrO3−)

A graft copolymer based on a polysaccharide (sodium salt of carboxymethylcellulose) and a vinyl monomer (acrylamide) has been synthesized in a nitrogen atmosphere, and its reaction conditions have been optimized for a better yield with ferrous sulfate and potassium bromate as a redox initiator. The effects of ferrous ion, bromate ion, hydrogen ion, sodium carboxymethylcellulose, and acrylamide along with the reaction time and temperature have been studied through the determination of the grafting parameters: the grafting ratio, add‐on, conversion, efficiency, homopolymer, and rate of grafting. The maximum yield has been found to occur when the acrylamide concentration is 8.0 × 10^?2 mol/dm³, whereas the maximum conversion occurs at a minimum concentration of acrylamide, that is, at 3.0 × 10^?2 mol/dm³. The grafting parameters have been found to increase with an increasing concentration of the redox initiator (Fe²⁺, from 2.0 × 10^?3 to 10.0 × 10^?3 mol/dm³; BrO, from 2.2 × 10^?3 to 4.0 × 10^?3 mol/dm³). The maximum efficiency occurs with a reaction time of 210 min. The rate of grafting has been found to be maximum up to 60 min; after that, it decreases rapidly. In this article, it is shown that the hydrogen ion leads to a very clear decrease in the grafting parameters as its concentration increases from 2.1 × 10^?3 to 11.3 × 10^?3 mol/dm³. Grafted gum and ungrafted gum have been characterized with Fourier transform infrared spectroscopy and thermogravimetric analysis. A probable mechanism has been suggested for graft copolymerization. It has been observed that the graft copolymer is thermally more stable than the parent backbone. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

The effect of temperature on limiting current density and mass transfer in electrodialysis

This study focuses on a high-temperature operation in electrodialysis of salt solutions and studies the effect of temperature on limiting current density and mass transfer. Experiments were conducted under various conditions of temperature (T), varying from 15 to 90°C; of dialysate concentration (C_d), varying from 5 × 10^?3 to 3 × 10^?2M ; and of dialysate velocity (u_d), varying from 0.206 to 2.44 cm s^?1. A least squares fitting of the experimental data on limiting current density (I_lim) yields an Arrhenius equation as follows: The molar flux N? (mol cm^?2 s^?1), initial concentration (C₀; M ) and temperature (T; °C) were found to have the following relationship: N?/C₀ is slightly increased with increasing temperature ranging from 25 to 70°C.     

Graft copolymerization of acrylamide onto cellulose in presence of comonomer using ceric ammonium nitrate as initiator

The graft copolymerization of acrylamide (AAm) and ethylmethacrylate (EMA) monomers onto cellulose has been carried out using ceric ammonium nitrate (CAN) as initiator in presence of nitric acid at (25 ± 1)°C and varying feed molarity from 7.5 × 10^?2 mol dm^?3 to 60.0 × 10^?2 mol dm^?3 at fixed feed composition (f_AAm = 0.6). The graft yield (%G_Y) has shown a linear increasing trend upto a feed molarity of 37.5 × 10^?2 mol dm^?3. The composition of grafted copolymer chains was found to be constant (F_AAm = 0.56) during feed molarity variation but shown variations with feed composition (f_AAm) and reaction temperature. The grafting parameters have shown increasing trends up to 7.5 × 10^?3 mol dm^?3 concentration of ceric (IV) ions and decreased on further increasing the concentration of ceric (IV) ions beyond 7.5 × 10^?3 mol dm^?3. The IR and elemental analysis data were used to determine the composition of grafted chains (F_AAm) and reactivity ratio of acrylamide (r₁) and ethylmethacrylate (r₂) comonomers. The reactivity ratio for acrylamide (r₁) and ethylmethacrylate (r₂) has been found to be 0.7 and 1.0 respectively, which suggested for an alternate arrangement of average sequence length of acrylamide (mM?₁) and ethylmethacrylate (mM?₂) in grafted chains. The rate of graft copolymerization of comonomers onto cellulose was found to be proportional to square concentration of comonomers and square root to the concentration of ceric (IV) ions. The energy of activation (ΔEa) of graft copolymerization was found to be 9.57 kJ mol^?1 within the temperature range of 20–50°C. On the basis of experimental findings, suitable reaction steps have been proposed for graft copolymerization of selected comonomers. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2546–2558, 2006     

Synthesis and characterization of maleylated cellulose-<Emphasis Type="Italic">g</Emphasis>-polyacrylamide hydrogel using TiO<Subscript>2</Subscript> nanoparticles under sunlight

Graft polymerization onto the cellulose is one way to produce semisynthetic copolymers and semiconductors were hardly used as initiators. Maleylated cellulose (MC) with different degree of carboxyl groups was synthesized and degree of carboxyl groups was determined using titration method. Then the graft copolymers of acrylamide (AM) on MC were synthesized by titanium dioxide semiconductor photoinitiator in aqueous suspension under sunlight. The effect of different parameters, such as the degree of carboxyl groups, degassing of atmosphere, reactor type, light source, MC/AM ratio, and initiator concentration, was evaluated in the synthesis of graft copolymers. MC with a high degree of carboxyl groups about 2.8 mmol g^?1 was selected for graft photopolymerization. Maximum monomer conversion (55%) for Maleylated cellulose-g-polyacrylamide (MC-g-PAM) was achieved with 0.5 mg TiO₂, MC/AM = 0.056, argon atmosphere, sunlight source, and double quartz tube reactor. The maximum amount of equilibrium swelling (41 g g^?1) was achieved for MC-g-PAM with 34% monomer conversion. The resulting graft copolymers were characterized by FT-IR, SEM, and TGA. Synthesis of MC-g-PAM using TiO₂ nanoparticles (NPs) as the initiator was done successfully that shows the TiO₂ NPs are useable in graft polymerization of acrylamide monomers onto the MC under sunlight.     

Grafting of styrene onto poly(butyl acrylate) in emulsion

The effect of time, temperature, the concentration of initiator and emulsifier, and the ratio of starting polymer to monomer on the degree of conversion (MC) of styrene and the grafting efficiency (GE) of polystyrene has been investigated. The reaction was initiated with potassium persulphate. It has been found that the degree of conversion of styrene and the grafting efficiency change in opposite directions when plotted as functions of the reaction parameters studied. The graft copolymerization is assisted by short reaction times and weight ratios of poly(butyl acrylate) to styrene greater than unity. The results obtained suggest that higher grafting efficiencies are obtained when the concentration of emulsifier is below its c.m.c. (critical micellar concentration) value. When using two different anionic emulsifiers it has been observed that the effect of initiator concentration on the degree of conversion of styrene and the grafting efficiency is complicated. Both the quantities studied (MC and GE) exhibit extrema in the range of initiator concentration studied (3.7?33.3 × 10^?5 mol dm^?3 of H₂O). No meaningful effect of temperature in the range 60°–90°C or that of dodecyl mercaptan (molecular weight regulator) used in an amount 0–0.4% in relation to poly(butyl acrylate) and styrene has been observed on the MC and GE values.     

Mechanism of the emulsion polymerization of methyl acrylate: 1. Initiation

The emulsion polymerization of methyl acrylate (MA) has been carried out under two different experimental conditions so as to establish the mode of chain initiation. In the first system, the initiator was Fenton's reagent (FeSO₄ and H₂O₂ redox pair) in acid solution at 20°C in the presence of a cationic detergent, cetyltrimethyl — ammonium bromide (CTAB), while in the second system the initiator was potassium persulphate (K₂S₂O₈) at 50°C in the presence of an anionic detergent, sodium lauryl sulphate (NaLS). The polymerization was followed by the conventional dilatometric and gravimetric methods. Initial rates were determined by keeping the conversion below 10% and by plotting the (yield/time) versus time, and extrapolating the straight line to zero time. It was found that in either case, Initial rate (v) ∝ (Initiator)^0.50 while the viscosity average molecular weight ($\text{M}{}_{\mathrm{v}}$) of the polymers up to 20% conversion was found to be approximately inversely proportional to the square root of the initiator concentration (I), i.e. $\text{(}\text{M}{}_{\mathrm{v}}\text{) ∝ (I)}{}^{\mathrm{?0.50}}$. The rate of polymerization up to 10% conversion was found to be approximately linear with the monomer concentration (from 0.5 to 5.0—, v/v) in the presence of detergents (above CMC) [critical monomer concentration] under the experimental conditions. Since the kinetics of the emulsion polymerization of MA at zero conversion are the same as that of the homogeneous polymerization of MA initiated by the free radicals, it is suggested that the initiation of the emulsion polymerization of MA takes place in the aqueous phase with little or no initiation in the detergent micelles containing monomer. If the polymerization is carried out within the solubility range of MA in the aqueous phase, then the initiation will take place entirely in the aqueous phase. Assuming homogeneous polymerization at zero conversion, the value of the termination rate constant (k_t) has been extracted from the experimental data at different initiator efficiencies.     

Photopolymerization of methyl methacrylate with the triethylamine-bromine charge transfer complex as photoinitiator

The triethylamine-bromine (TEA-Br₂) charge transfer complex was employed as photoinitiator in the photopolymerization of methyl methacrylate under light of 440 nm. The initial rate of conversion was 0.418%/min with an induction period of 56 min. The initiator and monomer exponents were 0.5 and 1.0, respectively. The polymerization was inhibited in the presence of hydroquinone but oxygen had a very little inhibitory effect. The value of k/k_t was 5.13 · 10^?2 l/mol · s and the activation energy was 19.18 kJ/mol. The rate constant for the decomposition of the charge transfer complex (k_ε) was 4.61 · 10^?6 1/s. Kinetic data and other evidence indicate that the overall polymerization takes place by a radical mechanism.     

Kinetic study of radical polymerization. VII. Investigation into the solution copolymerization of acrylonitrile and itaconic acid by real‐time 1H NMR spectroscopy

Free radical solution copolymerization of acrylonitrile (AN) and itaconic acid (IA) was performed with DMSO‐d₆ as the solvent and 2,2′‐azobisisobutyronitrile (AIBN) as the initiator. Weight ratio of the monomers to solvent and molar ratio of initiator to monomers were constant in all experiments. The initial comonomer composition was the only variable in this study. On‐line ¹H NMR spectroscopy was applied to follow individual monomer conversion. Mole fraction of AN and IA in the reaction mixture (f) and in the copolymer chain (F) were measured with progress of the copolymerization reaction. Overall monomer conversion versus time and also compositions of monomer mixture and copolymer as a function of overall monomer conversion were calculated from the data of individual monomer conversion versus time. Total rate constant for the copolymerization reaction was calculated by using the overall monomer conversion versus time data and then k_p/k_t^0.5 was estimated. The dependency of k_p/k_t^0.5 on IA concentration was studied and it was found that this ratio decreases by increasing the mole fraction of IA in the initial feed. The variation of comonomer and copolymer compositions as a function of overall monomer conversion was calculated theoretically by the terminal model equations and compared with the experimental data. Instantaneous copolymer composition curve showed the formation of alternating copolymer chain during copolymerization reaction. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3253–3260, 2007     

Protein hydrolysis under anaerobic,saline conditions in presence of acetic acid

The hydrolysis of soluble proteins in an anaerobic, saline (24 g dm^?3 NaCl) and mesophilic (37 °C) environment was studied. The inhibitory effect of a volatile fatty acid, acetic acid (HAc), on the hydrolysis rate and hydrolytic biomass activity for a model saline wastewater with a high protein load (total organic carbon, 1153 mg dm^?3 and 1572 mg dm^?3 proteins) was studied. Initial inhibitor concentrations were tested in the range of 0–2000 mg dm^?3 HAc. The microbiological characterization was performed using a total microorganism count by epifluorescence, and hydrolytic bacterial activity was determined by plate count. The protein hydrolysis was modeled according to first order kinetics. The effect of biomass on hydrolysis was analyzed by varying its concentration in the range of 42–210 mg dm^?3 volatile suspended solids. The following apparent hydrolysis kinetic constants (K_h) for proteins at 37 °C were obtained: 1.3, 0.8, 0.6, 0.2 and 0.1 d^?1 for initial concentrations of 250, 500, 750, 880, and 1000 mg dm^?3 HAc, respectively. At concentrations of HAc greater than 1000 mg dm^?3, total inhibition of hydrolysis was observed. The intrinsic hydrolysis constant ( ) at 37 °C, without inhibition, was 2.3 d^?1. The hydrolysis kinetic constant was not affected by the biomass concentration. The hydrolysis kinetics constant was filted to three models: Luong, Levenspiel and non‐competitive inhibition. The model that best represented the experimental data was Luong, obtaining an inhibition constant (K_I) of 1087 mg dm^?3 of HAc and the exponent γ = 0.54. The hydrolysis was inhibited by the presence of HAc, which corresponds to an intermediate compound of the anaerobic process. Copyright © 2004 Society of Chemical Industry     

Thermal decomposition of potassium persulfate in aqueous solution at 50°C in an inert atmosphere of nitrogen in the presence of acrylonitrile monomer

The rate of thermal decomposition of persulfate in aqueous solution in the presence of acrylonitrile (AN) monomer (M) and of nitrogen, may be written as: in the concentration range of persulfate (1.8 to 18.0) ×10^-3, and of monomer (M), 0.30 to 1.20, mol dm^-3. It was observed that the pH of the solution containing persulfate and monomer did not alter during polymerization if the monomer concentrations were close to its solubility under the experimental conditions. Conductance of the aqueous solutions of persulfate and monomer was found to decrease during the reactions. In an unbuffered aqueous solution containing only persulfate, however, the pH was found to decrease continuously at 50°C with time, while the conductance of the solution was found to increase. The monomer (AN) had no effect on the glass electrodes of the pH meter in aqueous solutions, and also on the electrodes of the conductivity cell. It has been suggested that the secondary or induced decompositions of persulfate were due to the following elementary reactions: where (M_j^· radicals (j = 1 to 10) are water-soluble oligomeric or polymeric free radicals. k_x and k_y at 50°C have been estimated as 1.70 X 10^-5 and 5.08 × 10³ dm³ mol^-1 s^-1, respectively. By measuring pH of freshly prepared persulfate solutions at 25°C, it is suggested that 0.05–0.30% of persulfate reacts molecularly with water (i.e., hydrolysis), as soon as it (10^-3 to 10^-2 mol dm^-3) is added to distilled water (pH 7.0). This hydrolysis was found to be stopped in dilute sulfuric acid solution (pH 3–4).     

Using 1H‐NMR spectroscopy for the kinetic study of the in situ solution free‐radical copolymerization of styrene and ethyl acrylate

The free‐radical copolymerization of styrene and ethyl acrylate in benzene‐d₆ as the solvent in the presence of benzoyl peroxide as an initiator at 70°C was studied by online ¹H‐NMR spectroscopy. The chemical composition of the copolymer at different reaction times was calculated from the conversion of the monomers to the copolymer, and then the reactivity ratios of styrene and ethyl acrylate were determined at both low and high conversions. Data for the overall monomer conversion versus the time were used to estimate the ratio k_pk_t^?0.5 for different compositions of the initial feed (k_p is the propagation rate constant, and k_t is the termination rate constant). k_pk increased with an increasing molar fraction of ethyl acrylate in the initial feed. The monomer mixture and copolymer compositions versus the overall monomer conversion were calculated with the data of ¹H‐NMR spectra. The incorporation of the styrene monomer into the copolymer structure was more favored than that of the ethyl acrylate monomer. Reducing the molar fraction of styrene in the initial feed intensified this. Drawing the molar fraction of styrene (or ethyl acrylate) in the copolymer chains versus that in the initial feed showed a tendency of the system toward random copolymerization. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Kinetics and Mechanism of Potassium Persulphate/L-Serine Initiated Polymerization of Methylmethacrylate

The polymerization kinetics of methyl methacrylate with K₂S₂O₈/L-serine redox system has been investigated volumetrically at 35±0.1°C under nitrogen atmosphere acidic aqueous medium in DMF/H₂O mixture (50% v/v). The rates of polymerization were measured varying concentrations of the monomer, initiator, L-serine as well as temperature; and it was found to increase with increasing of both temperature and concentrations of monomer, initiator, and L-serine. The overall energy of activation (E _a ) has been calculated to be 29.48 kJ/mol from the Arrhenius plot in temperature range 25–50°C. The molecular weight of the polymer was determined by gel permeation chromatography (GPC). Based on kinetic studies and depending on the results obtained, a suitable reaction mechanism has been suggested and the rates of polymerization found to obey the following equation: V _p [methyl methacrylate]^1.09[L-serine]^1.03[K₂S₂O₈]^0.96.     

Denitrifying kinetics involving the distributed ratio of reductases

A suspended-growth batch reactor was used to denitrify synthetic wastewater containing various proportions of nitrate and nitrite. A competitive phenomenon between nitrate- and nitrite-reductase was studied utilizing various proportions of nitrate and nitrite in an anaerobic environment with a temperature of 30°C and methanol as carbon source. By using a non-linear regression technique, biokinetic constants of the maximum specific reduction rates of nitrate and nitrite (k₁, k₂) and the Monod half-saturation coefficients of nitrate and nitrite (K_s1, K_s2) for the proposed two-step denitrifying kinetics were 1·29 day^?1, 0·89 day^?1 and 14·3 mg NO-N dm^?3, 10.9 mg NO-N dm^?3, respectively. The result obtained from a series of chemostat studies indicated the Monod-type kinetic model was more accurate when the distributed ratio of nitrate- and nitrite-reductase in the proposed two-step denitrifying kinetics was taken into account.     

Synthesis of poly(propylene carbonate) from highly active,inexpensive achiral (Salph)Co(III)X as initiator and bis(triphenyl phosphine) iminium as co‐initiator

Copolymerization of carbon dioxide with racemic propylene oxide has been investigated in the presence of an inexpensive achiral (Salph)Co(III)X [Salph is N,N′‐bis(3,5‐di‐tert‐butylsalicylidene) phenylenediimine and X is pentaflorobenzoate] as initiator and [PPN]⁺Cl^? ([PPN] is bis(triphenylphosphine) iminium) as co‐initiator. Effects of monomer‐to‐initiator ratio, initiator/co‐initiator ratio, and reaction conditions like stirring rate, temperature, and pressure of CO₂ on the molecular weight, yield, and selectivity of poly(propylene carbonate) over propylene carbonate have been studied. The initiator used in the study has been found to be highly active at milder conditions of pressure and temperature, giving a product with maximum M_w of 14.8 × 10³ g/mol at 25 bar and 50°C. The conversion increases with an increase in stirring rate and then becomes almost constant at 1100 rpm and above, indicating that the reaction is no longer limited by mass transfer. The molecular weight M_w of the polymer has been found to increase with increasing monomer‐to‐initiator ratio up to 3000:1, but it starts decreasing with a further increase in monomer‐to‐initiator ratio, giving a polymer of lower M_w. The activity of the initiator is considerably affected by pressure, temperature, time, and amount of co‐initiator. The polymeric product has low polydispersity (near unity) with negligible formation of polypropylene oxide. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43099.     

Some properties of β-D-Glucosidase from Trichoderma harzianum C1R1

β-D-Glucosidase from Trichoderma harzianum C₁R₁ consists of several isocomponents having isoelectric points in the pH range of 4.85-7.50. All the components exhibit both cellobiase and 4-nitrophenyl β-D-glucosidase (4NPGase) activity. The enzyme affinity for cellobiose (K_m = 3.92 mmol dm^?3) is 14.5 times weaker than for 4NPG (K_m = 0.27 mmol dm^?3). The hydrolysis of both substrates is competitively inhibited by glucose, the inhibition of 4NPG hydrolysis (K₁ = 2.00 mmol dm^?3) being about 4.2 times stronger compared to the hydrolysis of cellobiose (K₁ = 8.43 mmol dm^?3). The 4NPG hydrolysis is also competitively inhibited by the presence of cellobiose and D-glucono-1,5-lactone (K_i(cellobiose) = 5.00 mmol dm^?3; K_{i(D-glucono-1,5-lactone}) = 22 μmol dm^?3). The optimal hydrolysis conditions are the same for both substrates (pH 4.5,55° C). The half-lives of thermal inactivation at 61° C are 27 and 10min for cellobiase and 4NPGase, respectively.