New syntheses of graft copolymers using the DPE-technique: ATRP graft copolymerization

Summary A new one-step synthesis of a set of macroinitiators for atom transfer radical polymerization (ATRP) via controlled radical polymerization is presented. The macroinitiators consist of methacrylate and p-chloromethylstyrene (CMS) and were synthesized by controlled radical polymerization in the presence of l,l-diphenylethylene (DPE) using azobisisobutyronitrile (AIBN) as initiator. The resulting macroinitiators were used for the ATRP of different methacrylates yielding graft copolymers which were characterized by SEC and NMR. Received: 25 July 2002/Revised version: 28 October 2002/ Accepted: 28 October 2002 Correspondence to Oskar Nuyken     

Controlled radical polymerization of styrene utilizing excellent radical capturing ability of diphenyl ditelluride

Summary The radical polymerization of styrene was investigated in the presence of diphenyl ditelluride (DPDTe) under varied conditions. In the polymerization without any radical initiator at higher temperature (125°C), the addition of DPDTe surely decreased the polymer molecular weight (M _n) while the polydispersity (M _w/M _n) was rather broad. The polymerization with benzoyl peroxide (BPO) as the initiator was also uncontrollable to afford polymers with broad M _w/M _n probably due to the redox side reaction of BPO with DPDTe. On the contrary, the precision control of M _n and the initiating end structure could be achieved by the polymerization with 2,2'-azobisisobutyronitrile (AIBN), that is, M _n increased in proportion to the molar ratio of monomer to initiator suggesting the suppression of bimolecular chain termination reactions by the excellent radical capturing ability of DPDTe. Received: 23 June 1999/Revised version: 11 August 1999/Accepted: 16 August 1999     

New AB or ABA type block copolymers: atom transfer radical polymerization (ATRP) of methyl methacrylate using iodine-terminated PVDFs as (macro)initiators

Summary PMMA homopolymer with CF₃(CF₂)₂CF₂- end group was prepared by the ATRP of MMA using CF₃(CF₂)₂CF₂-I as an initiator and copper(I) salts/bipy catalysts. This indicated the production of perfluorobutyl radicals by ATRP mechanism and successful polymerization by them. Di- and triblock copolymers were also prepared by the ATRP of MMA using iodine-terminated PVDF as (macro)initiators. The kinetic plots (ln[M]_o/[M] vs. time) showed nearly first-order with respect to monomer concentration and the M_n,NMR of block copolymers increased linearly with conversion. However, iodine-terminated PVDF showed low initiator efficiency because propagating rate was much faster than initiating rate Received: 6 September 1999/Revised version: 27 December 1999/Accepted: 28 December 1999     

Synthesis and characterization of copolymers with alternating 1,4-bis(5'-acetyl-2'-thienyl)benzene or 1,3-bis(5'-acetyl-2'-thienyl)benzene chromophore and disiloxane units

Summary Activated (Ph₃P)₃RuH₂CO (Ru) catalyzed copolymerization of 1,4-bis(5'-acetyl-2'-thienyl)benzene (I) and 1,3-divinyltetramethyldisiloxane (II) yields alt-copoly[3,3,5,5-tetramethyl-4-oxa-3,5-disila-1,7-heptanylene/2',2"-diacetyl-5',5"-(1,4-benzene)-3',3"-bis (thiophenylene)] (III). On the other hand, Ru catalyzed copolymerization of 1,3-bis(5'-acetyl-2'-thienyl)benzene (IV) and II fails. Nevertheless, Ru catalyzed reaction of IV with excess vinylpentamethyldisiloxane (V) yields 1,3-bis(4'-pentamethyldisiloxy-ethyl-5'-acetyl-2'-thienyl)benzene (VI). VI undergoes acid catalyzed siloxane equilibration polymerization to give alt-copoly[3,3,5,5-tetramethyl-4-oxa-3,5-disila-1,7-heptanylene/2',2"-diacetyl-5',5"-(1,3-benzene)-3',3"-bis(thiophenylene)] (VII) and hexamethyldisiloxane. Copolymers III and VII have been characterized. Received: 26 July 1999/Revised version: 12 October 1999/Accepted: 12 October 1999     

Steric and electronic effects on mesophase stability of segmented liquid crystalline polymers with arylazomethine pendant groups

Summary The kinetics of DL-lactide polymerization was studied in CH₂Cl₂ at 25°C and in toluene at 70°C with HAPENAlOMe, a new Schiff's base complex derived from 2-hydroxyacetophenone and ethylenediamine. A higher polymerization rate is observed with this initiator as compared to other previously reported Al-alkoxides complexes. The polymerization with HAPENAlOMe is also shown to be a living process in both solvents. Moreover, the polymerization proceeds to quite high conversion without significant occurrence of transesterification reactions as confirmed from ¹³C NMR and SEC analysis. Received: 4 October 1999/Accepted: 6 December 1999     

Amphiphilic networks. XIV

Summary The synthesis and characterization of novel amphiphilic networks based on dimethylacrylamide and crosslinked by methacrylate telechelic three-arm star polyisobutylene (?(PIB-MA)₃) are reported. The networks are characterized by two M _c's and possess “homogeneous” and “heterogeneous” crosslinks. The networks swell both in water and n-heptane which indicates a cocontinuous hydrophobic-hydrophilic microarchitecture. Water-swollen networks exhibit higher tensile strengths and elongations, than those made previously with linear MA-PIB-MA's of similar overall compositions (i.e., ∼1.0 versus ∼0.5 Mpa, and ∼300% versus ∼200%, respectively). The enhanced mechanical properties of the new networks are being exploited in biomedical applications. Received: 28 July 1999/Revised version: 25 October 1999/Accepted: 27 October 1999     

Microwave promoted synthesis of chitosan‐graft‐poly(acrylonitrile)

Using microwave (MW) irradiation, polyacrylonitrile was grafted onto chitosan with 170% grafting yield under homogeneous conditions in 1.5 min in the absence of any radical initiator or catalyst. Under similar conditions a maximum grafting of 105% could be achieved when the K₂S₂O₈/ascorbic acid redox system was used as radical initiator in a thermostatic water bath at 35 ± 2°C. The representative graft copolymer was characterized by Fourier transform infrared spectra, thermogravimetric analysis, and X‐ray diffraction measurement, taking chitosan as a reference. The effects of such reaction variables as monomer/chitosan concentration, MW power, and exposure time on the graft co polymerization were studied. A probable mechanism for grafting without the redox system under microwaves was proposed. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 820–825, 2005     

Copolymers of acrylic acid with 2‐acryloyloxyethyl 2,4‐dichlorophenoxyacetate: Synthesis and herbicide release

Free‐radical copolymerization of acrylic acid with 2‐acryloyloxyethyl 2,4‐dichlorophenoxyacetate using 1.0 mol/L 1,4‐dioxane solution and 1.5 × 10^?2 mol/L of 2,2′ azobisisobutyronitrile as initiator has been carried out at 50°C. In addition to low conversion solution experiments performed to estimate the monomer reactivity ratios, three different copolymerizations over the whole range of conversions have been made. Theoretical values of cumulative copolymer composition, determined by the Mayo‐Lewis terminal model, have been correlated with those experimentally obtained. Finally, the herbicide release in three different aqueous pH buffer solutions has been evaluated in heterogeneous phase. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4238–4244, 2006     

Atom transfer radical polymerization of styrene with FeCl2/acetic acid as the catalyst system

Summary Atom transfer radical polymerization with FeCl₂/CH₃COOH as the catalyst has been successfully implemented for styrene. Various initiators have been used, among which carbon tetrachloride is the most effective one. High molecular weight products were obtained when CCl₄ was used as the initiator, and the measured molecular weight was close to the calculated one. Block copolymerization (PS-b-PMMA) was performed to confirm the living/controlled nature of the polymerization. ¹H NMR was used to characterize the structure of the macromolecular initiator and the block copolymer. If other initiators, such as benzyl bromide, ethyl 2-bromopropionate and α-bromoethyl benzene, were used, the polymerization occurred at ambient temperature resulting in oligomer. The molecular weight of the oligomer approaches to 4600 (M_n,th= 10000). Thus acetic acid, which is cheaper and less toxicity, can be used as coordinative ligand in ATRP initiated by CCl₄ mediated by iron. Received: 13 March 2000/Revised version: 13 November 2000/Accepted: 20 November 2000     

Synthesis and characterization of N-phenylmaleimide-methylvinylisocyanate copolymers with polystyrene side chains

Summary N-Substitued maleimide-methylvinylisocyanate copolymers with high glass transition temperature (T_g) was prepared and reacted with 4-hydroxy TEMPO (4-hydroxy-2,2,6,6-tetramethyl piperidinoxy) to yield polymers possessing stable radical at the side chain. The resulting polymers behaved as polymeric counter radicals for the radical polymerization of styrene. Thus, stable free radical mediated polymerization at the side chain was achieved. The resulting graft copolymers were characterized by spectral and thermal analysis. Received: 6 October 1999/Revised version: 7 March 2000/Accepted: 7 March 2000     

Free Radical Polymerization of Acrylonitrile Using Potassium Peroxy Disulphate Initiator and a Phase Transfer Catalyst

Free radical polymerization of acrylonitrile with the di-site phase transfer catalyst 1,4-bis(tetramethylhexyl)ethylenediammonium bromide (TMHEDAB) was investigated using the water-soluble initiator PDS (potassium peroxydisulphate) and water-insoluble solvent ethylacetate in an aqueous-organic biphase system at 60±1°C under nitrogen atmosphere at fixed pH and ionic strength. Rp increased with the increase in concentration of the monomer, initiator and catalyst. The order of R_p, with respect to monomer and catalyst concentration was found to be unity and with respect to initiator was found to be 0.5. A suitable mechanism has been proposed and its significance was discussed. The polymers obtained were characterized by spectral studies such as FTIR, ¹H-NMR, XRD, DSC, and TGA.     

Kinetic investigation of the radical polymerization of N-acryloylpiperidine in solution

The kinetics of free radical polymerizations of N-acryloylpiperidine (NAPi) were studied in benzene (Bz) using 2,2′-azobisisobutyronitrile (AIBN) as initiator. The activation energy was determined to be 111.7 kJ mol^?1. The overall rate of polymerization of the NAPi-AIBN-Bz system at 60°C was investigated as a function of monomer and initiator concentrations. Deviation from normal kinetics was observed with an order of 1.48 with respect to the monomer. The observed dependence of the rate constants k_p/k on monomer concentration could not be explained by the diffusion theory or the theory of electron donor-acceptor (EDA) complexes. The observed data have, however, been satisfactorily interpreted by the ‘hot’ radical theory.     

Novel non-alternating copolymers synthesized by spontaneous copolymerization of p-chlorophenylmaleimide with 2-methyl-2-oxazoline

Summary The copolymerization of p-chlorophenylmaleimide (1) as electrophilic monomer with 2-methyl-2-oxazoline (2) as nucleophilic monomer without initiator in solution under different experimental conditions was investigated. Copolymers were characterized by FT-IR and ¹H-NMR spectroscopy. The copolymer composition was determined from ¹H-NMR spectra. Molecular weights ranged between 1700 and 5400 g/mol by vapor pressure osmometry. Received: 27 September 1998/Revised version: 27 January 1999/Accepted: 28 January 1999     

Polymerization of acrylonitrile using potassium peroxydisulfate as an initiator in the presence of a multisite phase‐transfer catalyst: A kinetic study

In this article, the kinetics and mechanism of the free‐radical polymerization of acrylonitrile (AN) using potassium peroxydisulfate (PDS) as a water‐soluble initiator in the presence of synthesized 1,4‐bis(triethyl methyl ammonium) benzene dichloride (DC‐X) as a phase‐transfer catalyst (PTC) were studied. The polymerization reactions were carried out under inert and unstirred conditions at a constant temperature of 60 ± 1°C in cyclohexane/water biphasic media. The rate of polymerization (R_p) increased with an increase in the concentrations of AN, PTC, and PDS. The order with respect to the monomer, initiator, and PTC was found to be 1.0, 0.5, and 0.5, respectively. R_p was independent of the ionic strength and pH of the medium. However, an increase in the polarity of the solvent slightly increased the R_p value. On the basis of the obtained results, a mechanism is proposed for the polymerization reaction. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Microwave enhanced synthesis of chitosan-graft-polyacrylamide

Chitosan-graft-polyacrylamide (Ch-g-PAM) was synthesized without any radical initiator or catalyst using microwave (MW) irradiation. Under optimal grafting conditions, 169% grafting was observed at 80% MW power in 1.16 min. Conventionally under similar conditions a maximum grafting of 82% could be achieved in 1 h using K₂S₂O₈/ascorbic acid as redox initiator coupled with Ag⁺ ions as catalyst and atmospheric oxygen as co-catalyst on a thermostatic water bath at 35±0.2 °C. The representative microwave synthesized graft copolymer was characterized by Fourier transform-infrared spectroscopy, thermo gravimetric analysis and X-ray diffraction measurement, taking chitosan as a reference. The effects of reaction variables as monomer/chitosan concentration, MW power and exposure time on the graft co-polymerization were studied. A probable free radical mechanism for grafting under microwaves has been proposed. The solubility pH for the grafted samples with different extent of grafting was monitored. The adsorption capacity of chitosan was much enhanced after grafting. The microwave synthesized Ch-g-PAM in comparison to that prepared conventionally was found to have much more adsorption ability for Ca²⁺ and Zn²⁺ ions in aqueous solution.     

Photograft copolymerization of methyl methacrylate on silk fiber using titanium(III) chloride–potassium persulphate redox initiator in a limited aqueous system. I

Graft copolymerization of methyl methacrylate (MMA) onto mulberry silk fibers has been investigated in a limited aqueous system employing titanium(III) chloride–K₂S₂O₈ as the redox initiator under a photoactive condition with visible light. Polymerization in the presence of light at 32 ± 1°C has been found to be more pronounced than in the dark under identical conditions. The percentage of grafting, the percentage of total conversion, and the percentage of grafting efficiency have been studied by varying the reaction time, concentration of monomer, initiator concentration, solvent composition, and pH of the medium. A high percentage of grafting (∼ 93%), high grafting efficiency (∼ 97%), and the percentage of total conversion (∼ 25%) have been obtained with little homopolymer formation. Characterization of the grafted fibers has been investigated by Fourier transform infrared spectroscopy and scanning electron microscopy. Finally, the reaction mechanism has been discussed by considering hydrogen bonding. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2187–2193, 1999     

Polymerization of Butyl Acrylate using Potassium Peroxy Disulfate as Initiator in the Presence of Phase Transfer Catalyst—A Kinetic Study

The kinetics and mechanism of free radical polymerization of butyl acrylate (BA), using potassium peroxydisulfate (K₂S₂O₈) as initiator in the presence of propiophenonebenzyldimethylammonium chloride (PPBDMAC) as phase transfer catalyst (PTC) has been studied. The reactions were carried out under inert, unstirred conditions and at a constant temperature of 60°C in cyclohexanone/water biphase media. The dependence of the rate of polymerization (R_p) on various experimental conditions such as different concentrations of monomer, initiator, phase transfer catalyst, varying acid and ionic strength, temperature, and volume fraction of aqueous phase were studied. The order with respect to monomer, initiator, and the phase transfer catalyst were found to be 1.5, 0.5, and 0.5, respectively. The rate of polymerization was independent of acid and ionic strength. Based on the results, a mechanism has been proposed for the polymerization reaction.     

IRS study of ethylene polymerization catalyst SiO2/MAO/zirconocene

Summary Lewis acidic sites (LAS) of silica, modified with TMA and MAO samples differed by TMA content, have been characterized by IR spectroscopy (CO adsorption as probe molecule at 77 K). Two types of LAS were found on the surface of silica modified with MAO and TMA: M LAS of moderate strength (ν_CO= 2204−2212 cm⁻¹) and weak W LAS (ν_CO= 2194 cm⁻¹). The concentration of these acidic sites has been estimated. It was shown by IRS study Cp₂ZrMe₂ interacts both with W LAS and M LAS. Correlation between the amount of M LAS and the activity of ethylene polymerization has been found. Received: 13 October 1998/Revised version: 10 June 1999/Accepted: 10 June 1999     

Glass transition temperature and thermal degradation of N-2-acryloyloxyethyl phthalimide copolymers

Summary Copolymers of methyl methacrylate, MMA, with N-2-acryloyloxyethyl phthalimide, AEP, have been prepared by free radical polymerization. Glass transition temperatures, T_g; and thermal degradation of homo and copolymers have been determined by differential scanning calorimetry and by thermogravimetric analysis. Johnston's equation, which considers the influence of monomeric units' distribution on the copolymers glass transition temperature, has been used to explain the T_g behavior. The T_g12 has been calculated by the application of Johnston=s equation, given a value sensibly lower than the corresponding homopolymers T_g. The thermal stability of copolymers depends on the composition of the copolymer. Received: 30 May 2000/Revised version: 19 October 2000/Accepted: 19 October 2000     

Bulk functional oligomerization of ɛ-caprolactone in a mini extruder

Summary ɛ-caprolactone has been polymerized in bulk in a mini-extruder with Al(OiPr)₃ as initiator and benzyl alcohol as transfer agent. Polymer chains have been characterized by ¹H NMR, SEC and Maldi-Tof mass spectroscopy in order to investigate the potentialities of this process in terms of macromolecular engineering. Low temperatures around 75°C are enough to perform oligomerization at high conversion with a mean residence time less than 2 minutes. All the polymer chains are actually functionalized by the chemical group issued from the transfer agent. Molecular weight distribution depends on the temperature as well as on the residence time. Received: 3 October 2001/Revised version: 18 February 2002/ Accepted: 7 M?rz 2002