Multiblock copolymers by polymeric initiators via free radical mechanism

Polymeric peroxycarbamate initiators containing polyazoester or polyethylene adipate blocks were synthesized. They can be used to prepare multiblock copolymers by radical polymerization in a procedure involving several steps. Bulk and solution polymerizations are suitable techniques in these steps. The polymerization of styrene with these initiators was investigated over a wide range of conversion. Longer polymerization times led to an expected decrease in peroxygen contents of the active polystyrenes. Styrene/methyl methacrylate/n-butyl methacrylate, polyethylene adipate/styrene/methyl methacrylate, polyethylene adipate/styrene/methyl methacrylate/n-butyl methacrylate and polyethylene adipate/styrene/methyl methacrylate/acrylonitrile multiblock copolymers were obtained in this way.     

Poly(methyl methacrylate)–cellulose nitrate copolymers. I. Preparation

Poly(methyl methacrylate)–cellulose nitrate copolymers were prepared in the form of rods and sheets by bulk polymerization using benzoyl peroxide as initiator. Suspension polymerization did not succeed in preparing poly(methyl methacrylate)–cellulose nitrate copolymers, especially when cellulose nitrate of 11.4% nitrogen content was used. The parameters such as cellulose nitrate concentration, nitrogen content of cellulose nitrate, the amount of initiator and the reaction time, and the temperature are discussed. The prepared copolymers were irradiated for specified periods of up to 11.83 Mrad. It was found that poly(methyl methacrylate)–cellulose nitrate copolymers did not dissolve in any conventional solvent, but they swelled. Swelling decreases with increasing cellulose nitrate concentrations, nitrogen content of cellulose nitrate, and irradiation dose, indicating the crosslinked structure of the prepared copolymers.     

四官能度过氧化物JWEB50引发的PS-b-PMMA合成与表征

引言嵌段共聚物是具有两种或两种以上不同链段的聚合物,不同链段间存在的化学键限制了聚合物的相分离程度,易形成微相分离结构[1],而嵌段共聚物能作为聚合物共混体系的相容剂,只需加入少量     

Block copolymers obtained by free-radical mechanism. I. Methyl methacrylate and styrene

Block copolymers were synthesized using styrene and methyl methacrylate as the monomers and a multifunctional initiator, di-t-butyl 4,4′-azobis(4-cyanoperoxyvalerate). The unique feature of this sequential initiator is the fact that the formation of the free radicals can be achieved thermally and/or by a redox system at different stages. The polymerizations for the formation of the block copolymer were carried out in two stages. First, a polymeric initiator was synthesized, which was then used in the second stage to initiate the polymerization of the second monomer. Styrene and methyl methacrylate were used as the comonomers. Selective solvent fractionation was used for the separation of the block from the homopolymers. The separation technique was found to be efficient, giving pure block copolymers which could subsequently be characterized by GPC, NMR, IR, and EM techniques.     

Application of A4F-MALS for the Characterization of Polymers Prepared by Emulsion Polymerization: Comparison of the Molecular Structure of Styrene-Acrylate and Methyl Methacrylate-Acrylate Copolymers

In this paper, organic asymmetric flow field flow fractionation coupled to a multi-angle light scattering detector is presented as a very efficient tool for the characterization of copolymers prepared by emulsion polymerization. The molar mass distribution and the extent of branching of styrene–acrylate copolymers have been compared with corresponding copolymers of methyl methacrylate. It has been found that the presence of acrylate monomer results in the increase of molar mass and formation of branched macromolecules due to intermolecular chain transfer to polymer similarly as in case of methyl methacrylate–acrylate copolymers. However, the effect is far less pronounced.     

Adjustable wettability of methyl methacrylate modified ramie fiber

The surface hydrophobicity/hydrophilicity of ramie fiber was regulated through the atom transfer radical polymerization of methyl methacrylate from initiators immobilized on the fiber. The optimal reaction conditions for preparing the macroinitiated ramie fiber were determined to be a temperature of 60°C and a reaction time of 24 h. The grafted copolymers were characterized by Fourier transform infrared spectroscopy, X‐ray diffraction, scanning electron microscopy, energy‐dispersive analysis of X‐rays, gel permeation chromatography, and thermogravimetric analysis. The results indicate that poly (methyl methacrylate) was covalently bonded onto the surface of the ramie fiber, and the polymerization of methyl methacrylate was a living/controlled process under the investigated conditions. The results of the contact angle measurements indicate that the wettability of the ramie fiber could be widely regulated by control of the grafted ratios of poly(methyl methacrylate) from 26 to 33 wt %. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Vinyl Polymerization. 218. Polymerization of Methyl Methacrylate in the Presence of Nylon-6 Fiber and Water

The polymerization of methyl methacrylate in the presence of nylon-6 fibers and water was carried out. It was found that the conversion in the absence of water was the same as that of thermal polymerization, but in the presence of water the conversion was much higher. When methyl methacrylate and water existed sufficiently in the polymerization system, the rate of polymerization (R_p) was given by the following equation; R_p = k (Nylon)^1,0 (Methyl methacrylate)⁰ (Water)⁰. The over-all activation energy of the polymerization was found to be 13 kcal/mole. The polymerization of styrene, acrylonitrile, vinyl acetate, and methyl acrylate could not be initiated by the system of nylon and water. Apparent grafting efficiency of polymethyl methacrylate onto nylon was calculated from the amount of polymer which was not extracted with acetone. The efficiency was independent on the reaction time and the amount of water, and increased with the amount of nylon, while it decreased with the amount of methyl methacrylate and with reaction temperature. From the fact that a major part of the polymethyl methacrylate could not be extracted, it was concluded that the polymerization of methyl methacrylate in the presence of nylon and water occured predominantly inside the fiber. The degree of the polymerization of polymethyl methacrylate formed inside the nylon fiber was considerably higher than that of homopolymethyl methacrylate formed outside the fiber. It was qualitatively recognized that the major part of the polymethyl methacrylate generated in the fiber was not grafted onto nylon, but existed as homopolymer.     

Synthesis of ABA triblock copolymers of N-substituted maleimides and methacrylates by group transfer polymerization

Summary ABA type block copolymerization of N-phenylmaleimide (NPM), N-hexyl maleimide (NHM), methyl methacrylate (MMA), and butyl methacrylate (BMA) was investigated by group transfer polymerization (GTP) with [1,5-bis (trimethylsilyloxy)-1,5-dimethoxy-1,4-pentadiene] (1) as difunctional initiator. A novel block copolymers (2) of NPM and MMA (or BMA) could be prepared by sequential addition of NPM to the living PMMA (or PBMA) produced with 1. The reaction did not exhibit the characteristics of living polymerization when NPM was added. The resulting copolymers showed good thermal stability. On the other hand, gelation occurred in GTP of NHM.     

Mechanochemical copolymerization of methyl methacrylate and styrene initiated by the grinding of quartz

The copolymerization of methyl methacrylate and styrene mechanochemically initiated by the grinding of quartz in the monomer mixture was investigated by using a vibrating ball mill. The effect of the grinding of quartz on the copolymerization was investigated by characterizing both the polymer formed and the ground quartz. The copolymerization proceeds apparently from the quartz grindings and was closely related to the total surface area of the ground quartz. The molecular weight distributions of the copolymers formed were unimodal as found in a homopolymer of only methyl methacrylate. It was clear from the composition analysis of the copolymer that the mechanochemical copolymerization of methyl methacrylate and styrene proceeded with a radical polymerization mechanism because of radicals on the quartz surface produced by the grinding. The monomer reactivity ratios obtained by the Fineman‐Ross method suggested that the copolymers formed were alternating copolymers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2011–2017, 2002; DOI 10.1002/app.10544     

Graft copolymerization of methyl methacrylate with an N‐substituted maleimide–liquid‐crystalline copolymer by atom transfer radical polymerization

The synthesis of novel copolymers consisting of a side‐group liquid‐crystalline backbone and poly (methyl methacrylate) grafts were realized by the use of atom transfer radical polymerization (ATRP). In the first stage, the bromine‐functional copolymers 6‐(4‐cyanobiphenyl‐4′‐oxy)hexyl acrylate and (2,5‐dioxo‐2,5‐dihydro‐1H‐pyrrole‐1‐yl)methyl 2‐bromopropanoate were synthesized by free‐radical polymerization. These copolymers were used as initiators in the ATRP of methyl methacrylate to yield graft copolymers. Both the macroinitiator and graft copolymers were characterized by ¹H‐NMR, gel permeation chromatography, differential scanning calorimetry, and thermogravimetric analysis. The ATRP graft copolymerization was supported by an increase in the molecular weight of the graft copolymers compared to that of the macroinitiator and also by their monomodal molecular weight distribution. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Stereoregular poly(alkyl methacrylate)s: polymer-polymer and copolymer-polymer blends

Amorphous blends of isotactic and syndiotactic poly(methyl methacrylate) were found to be compatible. To evaluate the interaction between these tactic polymers, random copolymers of isotactic poly(methyl/ethyl methacrylate) were blended with syndiotactic poly(methyl methacrylate). Only the copolymers with an ethyl methacrylate content below 45% were compatible with syndiotactic poly(methyl methacrylate). Using a Flory-Huggins type treatment of copolymer mixtures, the segmental interaction parameters for poly(methyl methacrylate) with poly(ethyl methacrylate) and for isotactic with syndiotactic poly(methyl methacrylate) were calculated. The interaction parameter for the tactic poly(methyl methacrylate) pair was found to be small and negative.     

Lichtinduzierte Polymerisation, 4. Pfropfcopolymerisation von Methylmethacrylat auf Polyethylenoxid in Gegenwart von Chinolinderivaten

When using poly(ethylene oxide) (PEO) as a polymeric hydrogen donator, grafted polymerization products are obtained upon photoinduced polymerization of methyl methacrylate with quinoline derivatives and PEO. The separation of these graft copolymers from the simultaneously formed homopolymeric poly(methyl methacrylate) (PMMA) and the remainder of not converted PEO can be achieved by subsequent extraction with ethyl acetate and methanol. With that determination of graft yield, degree of grafting, grafting success, and grafting height are possible.     

Polymerization of methyl methacrylate with mechano-chemically synthesized macroinitiators

The polymerization of methyl methacrylate initiated by acrylonitrile- based homopolymers and copolymers synthesized mechanochemically by vibratory milling has been studied. The factors influencing the conversion and poly(methyl mehtacrylate) molecular weight are discussed. Both characteristics depend on polymerization parameters (reaction time, temperature and initiator concentration) as well as on macroinitiator synthesis conditions (duration of the vibratory milling process, comonomer ratio). The polymerization product consists of poly(methyl methacrylate) and small amounts of poly(acrylonitrile-g-methyl methacrylate)copolymer.     

Polyallene-based graft copolymer via 6-methyl-1,2-heptadien-4-ol and methyl methacrylate

A series of well-defined graft copolymers with a polyallene-based backbone and poly(methyl methacrylate) side chains were synthesized by the combination of living coordination polymerization of 6-methyl-1,2-heptadien-4-ol and atom transfer radical polymerization of methyl methacrylate. We first prepared poly(alcohol) with polyallene repeating units via 6-methyl-1,2-heptadien-4-ol by living coordination polymerization initiated by [(η³-allyl)NiOCOCF₃]₂, followed by transforming the pendant hydroxyl groups into halogen-containing ATRP initiation groups. Next, grafting-from route was used for the synthesis of the well-defined graft copolymer with excellent solubility: poly(methyl methacrylate) was grafted to the backbone via ATRP of methyl methacrylate. This kind of graft copolymer is the first example of graft copolymer via allene derivative and methacrylic monomer.     

Preparation of multiphase block copolymers by redox polymerization process, 4. Polymerization of methyl methacrylate by the redox system Mn(III)-poly(ethylene glycol) containing azo groups

Redox polymerization of methyl methacrylate using Mn(III) with poly(ethylene glycol) having azo and hydroxy functions was carried out to yield ethylene glycolmethyl methacrylate block copolymers with labile azo linkages in the main chain. These prepolymers were used to initiate free-radical polymerization of styrene through thermal decomposition of the azo groups, resulting in the formation of multiblock copolymers. Successful blocking has been confirmed by fractional precipitation, a strong change in the molecular weight, and spectral measurements.     

Synthesis and pH-dependent micellization of 2-(diisopropylamino)ethyl methacrylate based amphiphilic diblock copolymers via RAFT polymerization

The polymerization of 2-(diisopropylamino)ethyl methacrylate (DPA) by RAFT mechanism in the presence of 4-cyanopentanoic acid dithiobenzoate in 1,4-dioxane was studied. The DPA homopolymer was employed as a macro chain transfer agent to synthesize pH-sensitive amphiphilic block copolymers using poly(ethylene glycol) methyl ether methacrylate (PEGMA) as the hydrophilic block. ¹H NMR and GPC measurements confirmed the successful synthesis of these copolymers. Potentiometric titrations and fluorescence experiments proved that the copolymers underwent a sharp transition from unimers to micelles at a pH of ∼6.7 in phosphate buffered saline solutions. It was found that the hydrophilic/hydrophobic balance of these block copolymers had no apparent effect on their pH-induced micellization behaviors. The DLS investigation revealed that the micelles have a mean hydrodynamic diameter below 60 nm with a narrow size distribution.     

Synthesis of well‐defined comb‐like amphiphilic copolymers with protonizable units in the pendent chains: 2. Poly(2‐(dimethylamino)ethyl methacrylate) grafted poly(methyl methacrylate‐co‐2‐hydroxyethyl methacrylate) copolymers and their association behavior in aqueous solution

Narrow‐distribution, well‐defined comb‐like amphiphilic copolymers are reported in this work. The copolymers are composed of poly(methyl methacrylate‐co‐2‐hydroxyethyl methacrylate) (P(MMA‐co‐HEMA)) as the backbones and poly(2‐(dimethylamino)ethyl methacrylate) (PDMAEMA) as the grafted chains, with the copolymer backbones being synthesized via atom‐transfer radical polymerization (ATRP) and the grafted chains by oxyanionic polymerization. The copolymers were characterized by gel permeation chromatography (GPC), Fourier‐transform infrared (FT‐IR) spectroscopy and ¹H NMR spectroscopy. The aggregation behavior in aqueous solutions of the comb‐like amphiphilic copolymers was also investigated. ¹H NMR spectroscopic and surface tension measurements all indicated that the copolymers could form micelles in aqueous solutions and they possessed high surface activity. The results of dynamic light scattering (DLS) and scanning electron microscopy (SEM) investigations showed that the hydrodynamic diameters of the comb‐like amphiphilic copolymer aggregates increased with dilution. Because of the protonizable properties of the graft chains, the surface activity properties and micellar state can be easily modulated by variations in pH. Copyright © 2004 Society of Chemical Industry     

Polymerization kinetics of indene, methyl methacrylate and acrylonitrile and characterization of their terpolymer

The free radical terpolymerization of indene (In), methyl methacrylate (MMA) and acrylonitrile (AN) has been investigated. The rate of polymerization of all the binary systems involved has been measured dilatometrically for the homogeneous polymerization. The reactivity ratios of the three binary systems were calculated and were found to be equal to 0.031 and 0.397 for In/AN copolymers and 0.02 and 3.82 for In/MMA copolymers and finally 0.152 and 1.20 for AN/MMA copolymers. The rate of terpolymerization in bulk has been measured as well as the relationship between the monomer mixture composition and the obtained terpolymer in order to construct the compositional triangle. Also the effect of initiator concentration on the rate of terpolymerization was investigated. The activation energy of terpolymerization was determined. The terpolymers were characterized by spectral and thermo-gravimetric analyses. The data indicates that polyindene improves the thermal stability of the prepared terpolymers.     

Reactivity of N-alkylated cyclic imino ether salts having vinyl group

Summary Two copolymers of 2-isopropenyl-2-oxazolinium tetrafluoroborate with methyl methacrylate and with methyl acrylate were prepared, from which the polymerization of 2-oxazolines (2-methyl and 2-t-butyl) was initiated to prepare graft copolymers.     

Graft copolymers prepared by atom transfer radical polymerization (ATRP) from cellulose

A cellulose-based macro-initiator, cellulose 2-bromoisobutyrylate, for atom transfer radical polymerization (ATRP) was successfully synthesized by direct homogeneous acylation of cellulose in a room temperature ionic liquid, 1-allyl-3-methylimidazolium chloride, without using any catalysts and protecting group chemistry. ATRP of methyl methacrylate and styrene from the macro-initiator was then carried out. The synthesized cellulose graft copolymers were characterized by FTIR, ¹H NMR and ¹³C NMR spectroscopies. The grafted PMMA and PS chains were obtained by the hydrolysis of the cellulose backbone and analyzed by GPC. The results obtained from these analytical techniques confirm that the graft polymerization occurred from the cellulose backbone and the obtained copolymers had grafted polymer chains with well-controlled molecular weight and polydispersity. Through static and dynamic laser light scattering and TEM measurements, it was found that the cellulose graft copolymer in solution could aggregate and self-assembly into sphere-like polymeric structure.