Photochemical modification of the lower critical solution temperature of cinnamoylated poly(N‐2‐hydroxypropylmethacrylamide) in water

Partial modification of the nonionic polymer poly(N‐2‐hydroxy‐propylmethacrylamide) by cinnamate produces stimuli‐responsive copolymers. The hydrophobic character of the cinnamate chromophore induces not only a lower critical solution temperature (LCST) in water, but renders additionally the polymers photoresponsive. For moderate cinnamate contents of 9 mol‐%, the photoisomerization of the trans‐cinnamate to cis‐cinnamate groups allows to switch the LCST by irradiation, whereas for higher cinnamate contents of 21 mol‐%, irradiation leads to intra‐ and intermolecular photocrosslinking.     

Living cationic polymerization of a coumarin‐substituted vinyl ether and reversible photoinduced crosslinking of the resulting homopolymers and amphiphilic block copolymers

Living cationic polymerization of 4‐methyl‐7‐(2‐vinyloxyethoxy)coumarin (CMVE) was achieved using SnCl₄ in the presence of nBu₄NBr as an added salt at 0 °C. The number‐average molecular weight of the resulting polymers increased in direct proportion to the monomer conversion while retaining relatively low polydispersity. Structural analysis revealed that the resulting polymers carried pendant coumarinyl moieties. These coumarinyl moieties were crosslinked by irradiation with UV light at λ_max = 366 nm, and the crosslinked sites were then cleaved by irradiation with UV light at λ_max = 254 nm. The crosslinking behaviors of the polymers were studied by UV and FTIR spectroscopic measurement. PolyCMVE was soluble in dichloromethane but was found to be insoluble upon UV light irradiation. We also synthesized amphiphilic block polymers bearing coumarinyl moieties by living cationic copolymerization with an amphiphilic vinyl ether. The resulting block polymers were soluble in an aqueous medium and also formed micelle‐like aggregates. Upon UV irradiation of aqueous solutions above the critical micelle concentration, an efficient crosslinking reaction occurred. Photoinduced structural changes of these polymer aggregates in the solution state were further investigated. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Tag‐Convertible Photocrosslinker with Click‐On/Off N‐Acylsulfonamide Linkage for Protein Identification

The N‐acylsulfonamide group, known as a safety‐catch linker, has been applied to photoaffinity labeling (PAL) using a cinnamate‐type photocrosslinker to improve the efficiency of PAL‐based target identification. A bioorthogonal sulfo‐click reaction was used to stably link a photocrosslinker unit with N‐acylsulfonamide linkage to produce a photoactivatable probe without any protection. In addition, the crosslinked protein was selectively isolated with a small cinnamate tag via linkage disruption upon N‐alkylation. Furthermore, the tag moiety was photochemically converted to a stable coumarin derivative by losing a water molecule, which is a useful property in MS‐based identification.     

Synthesis and photocrosslinking of maleimide-type polymers

Self-sensitizable photocrosslinking maleimide-type polymers were synthesized by using (N-cinnamoyloxymethyl)maleimide ( 1 ) as a maleimide having a photodimerizable group, nitrophenyl acrylate as a sensitizer monomer, and styrene or methyl acrylate. The fluorescence spectra of these polymers exhibit an excimer band around 455 nm. The excimer intensity of the polymers decreased mainly during the early irradiation time. This decreasing tendency was similar to the increasing tendency of the insoluble fractions of the polymers with irradiation time. These results suggest that the photocrosslinking reaction of the polymers occurs via an excimer formation of the cinnamoyl groups and can be traced by fluorescence spectroscopy.     

Effects of the acid chain length and copolymer crosslinking on the acylation of N-hydroxysuccinimide copolymers with carbobenzoxyoligo-ϵ-aminocaproic acids

N-Hydroxysuccinimide-type soluble copolymer with styrene and three similar divinylbenzene (3–4 mole-%) crosslinked copolymers with styrene, N-vinylpyrrolidone, and N,N-dimethylacrylamide were prepared from their precursor copolymers of N-acetoxymaleimide. Acylation of these N-hydroxyl polymers with carbobenzoxyoligo-?-aminocaproic acids was conducted in dimethylformamide at room temperature by using dicyclohexylcarbodiimide as condensing agent. The soluble styrene copolymer was acylated in good conversions (76–89%) in every case (n = 1–3), whereas the acylation of the crosslinked copolymers decreased slightly from n = 1 to n = 2, and dropped suddenly to only small conversions (4.7–7.4%) with n = 3, showing a marked inhibitory effect of crosslinking when the acids became longer. The effect of the microenvironment of the polymer did not appear significant. All the acyl polymers, including the precursor polymers, yielded the corresponding cyclohexylamides when treated with cyclohexylamine.     

Optimal irradiation wavelength in iniferter‐based photocontrolled radical polymerization

In iniferter‐based photocontrolled radical polymerization optimal irradiation wavelength was examined for precise molecular design of star vectors, which can function as high‐performance gene carriers. Monochromatic light in the range from 330 to 400 nm with the interval of about 10 nm was irradiated to tetrafunctional iniferter, 1,2,4,5‐tetrakis(N,N‐diethyldithiocarbamylmethyl)benzene, in the presence of N,N‐dimethyaminopropylacrylamide (DMAPAAm), as a model monomer, in toluene. In all wavelengths tetrabranched polymers were produced except for 400‐nm‐irradiation. The highest conversion reaching to about 35% was observed at the wavelength of 370 nm after only 40 min of irradiation. There was no further increase in conversion by combination with another two wavelengths. HPLC analysis and NMR spectra showed that the polymerization at the optimal wavelength of 370 nm was occurred in a living manner with the ability to control the chain length (from about 5000 to 40,000) having very narrow polydispersity (about 1.6) by changing of the irradiation time, the intensity, and the monomer concentration. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4505–4512, 2008     

Swelling–shrinking behaviors of poly(N-isopropylacrylamide) and poly(N-n-propylacrylamide) gels prepared by chemical and radiation crosslinking methods

The swelling and shrinking kinetics of thermosensitive gels based on N-isopropylacrylamide (NiPAAm) and N-n-propylacrylamide (NnPAAm) were studied. Four gels cylindrical in shape were prepared by two different methods: γ-ray irradiation to aqueous solutions of poly(NiPAAm) (PNiPAAm) or poly(NnPAAm) (PNnPAAm) and redox polymerization of NiPAAm or NnPAAm monomer using N,N′-methylenebisacrylamide as a crosslinker. There were a few differences in the swelling kinetics among these gels. However, a marked difference was observed in the shrinking processes, the rate of which was faster in the order of radiation-crosslinked PNiPAAm gel > radiation-crosslinked PNnPAAm gel > chemically crosslinked PNnPAAm gel > chemically crosslinked PNiPAAm gel. This difference was discussed in terms of the microscopic structure of the gels, which was studied by light scattering techniques. It was found that the static inhomogeneities frozen in the chemically and radiation-crosslinked gels play a key role in their shrinking kinetics.     

Preparation of intermediary layer crosslinked micelles from a photocrosslinkable amphiphilic ABC triblock copolymer

To prepare intermediary layer crosslinked micelles, a photocrosslinkable amphiphilic ABC triblock copolymer, poly(ethylene glycol)-b-poly(2-cinnamoyloxyethyl methacrylate)-b-poly(methyl methacrylate) (PEG-PCEMA-PMMA), was synthesized and its micellar characteristics were investigated. The triblock copolymer of PEG-b-poly(2-hydroxyethyl methacrylate)-b-PMMA (PEG-PHEMA-PMMA) (M_n = 9800 g/mol, M_w/M_n = 1.33) was first polymerized by activators generated by electron transfer (AGET) atom transfer radical polymerization (ATRP) using a PEG macroinitiator in a mixed solvent of anisole/2-isopropanol (3/1 v/v). The middle block of the copolymer was then functionalized with cinnamoyl chloride. The degrees of polymerization of the PEG, PHEMA, and PMMA blocks were 113, 18 and 21, respectively. The critical micelle concentration (CMC) of the PEG-PCEMA-PMMA was 0.011 mg/mL. The PEG-PCEMA-PMMA micelles were spherically shaped with an average diameter of 43 nm. The intermediary layer of the PEG-PCEMA-PMMA micelles was crosslinked by UV irradiation. Not all of the cinnamate groups underwent photocrosslinking probably due to a lack of other cinnamate groups in their immediate vicinity. However, the degree of photocrosslinking of the intermediary layer of the PEG-PCEMA-PMMA micelles was sufficient to give excellent colloidal stability, even in different external environments.     

Quaternization of poly(tertiary aminostyrene)s and characterization of the quaternized polymers

The Menschutkin reaction of three poly(tertiary aminostyrene)s: poly(N,N-dimethyl-4-vinylphenylamine) (PPA), poly(N,N-dimethyl-4-vinylbenzylamine) (PBA), and poly(N,N-dimethyl-4-vinylphenethylamine) (PPTA) was investigated. These three polymers having narrow molecular weight distributions were prepared via anionic living polymerization. PPA reacted homogeneously with n-butyl bromide in N,N-dimethylformamide (DMF). PBA and PPTA also reacted homogeneously with n-butyl bromide in a mixture of DMF/methanol (75/25 v/v %). GPC measurement of the quaternized polymers was carried out using a mixture of water/acetonitrile (80/20 v/v %) containing 0.5M acetic acid and 0.3M sodium sulfate (pH = 2.9) as an eluant in order to suppress adsorption of the quaternized water soluble polymers on GPC gel. Results of GPC measurement indicate that the polymer chains of the three poly(tertiary aminostyrene)s are neither severed nor crosslinked in the process of quaternization. Temperature dependence and reaction time dependence on the degree of quaternization (DQ) were studied for PPT, PBA, and PPTA. By altering reaction time and temperature, the DQ values of the three poly(tertiary aminostyrene)s could be controlled in the range from 0% to nearly 100%. Quaternization reactivity of the amino groups in the three polymers was found to decrease in the order, PPTA, PBA, and PPA. The differences in reactivity are thought to be attributable to the electron density on the nitrogen atom of the N,N-dimethylamino group, and steric hindrance in the vicinity of the nitrogen atom. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1219–1226, 1997     

Photosensitive polymers with cinnamate units in the side position of chains: Synthesis, monomer reactivity ratios and photoreactivity

Ethyl α-cyano-4-(methacryloxy)cinnamate was synthesized to prepare new photosensitive polymers. Homopolymerization and copolymerizations were carried out in solution in chloroform at 65 °C using AIBN as an initiator. Methyl methacrylate was chosen as comonomer for the studies of copolymerzation. The structures formed were characterized by IR and ¹H NMR spectroscopies. The values of reactivity ratios of the comonomers calculated according to the Finneman-Ross method indicated that the reactivity of the synthesized photosensitive monomer is lower than that of MMA. Thin films of the obtained polymers were prepared to study their ability to crosslink under UV irradiation. The photodimerization of the cinnamate moieties was characterized.     

Surface-relief-grating formation behavior of two hyperbranched azo polymers

In this work,surface-relief-grating formation behavior was studied by using two hyperbranched azo polymers.The hyperbranched polymers containing pseudo-stilbene type azo chromophores throughout the hyperbranched structure were synthesized by step-growth polycondensation of AB₂ type monomers.The AB₂ monomer,4-（4’-（bis（2-chloroethyl）amino）-phenylazo） benzoic acid（BAA）,was prepared through azo-coupling reaction between N,N’-bis（2-chloroethyl）aniline and 4- aminobenzenic acid.The another AB₂ monomer,4-（4’-（bis（2-chloroethyl）amino）phenylazo）-3-nitro-benzoic acid（BANA）, was prepared through azo-coupling reaction between N,N-bis（2-chloroethyl）aniline and 3-nitro-4-aminobenzcnic acid.The hyperbranched polymers（PBAA and PBANA） were prepared through nucleophilic substitution reaction of BAA and BANA, respectively.The polymers synthesized were characterized by using spectroscopic methods and thermal analysis.The photoinduced dichroism and photo-induced surface-relief-grating（SRG） formation of the hyperbranched polymers were investigated upon irradiation with Ar⁺ laser at 488 nm.PBAA shows typical photoinduced dichroism SRG formation behavior.On the contrary,PBANA does not show the photoresponsive properties.The results indicate that the nitro at the ortho position of azo group of PBANA shows the effect of inhibiting the photoinduced variations.The effect can be attributed to the blockage of the trans-cis isomerization of the azobenzene moieties by the steric hindrance.     

Synthesis of silicon nitride based ceramic nanoparticles by the pyrolysis of silazane block copolymer micelles

Diblock copolymer poly(1,1,3,N,N′‐pentamethyl‐3‐vinylcyclodisilazane)‐block‐polystyrene (polyVSA‐b‐polySt) and triblock copolymer poly(1,1,3,N,N′‐pentamethyl‐3‐vinylcyclodisilazane)‐block‐polystyrene‐block‐poly(1,1,3,N,N′‐pentamethyl‐3‐vinylcyclodisilazane) (polyVSA‐b‐polySt‐b‐polyVSA), consisting of silazane and nonsilazane segments, were prepared by the living anionic polymerization of 1,1,3,N,N′‐pentamethyl‐3‐vinylcyclodisilazane and styrene. PolyVSA‐b‐polySt formed micelles having a poly(1,1,3,N,N′‐pentamethyl‐3‐vinylcyclodisilazane) (polyVSA) core in N,N‐dimethylformamide, whereas polyVSA‐b‐polySt and polyVSA‐b‐polySt‐b‐polyVSA formed micelles having a polyVSA shell in n‐heptane. The micelles with a polyVSA core were core‐crosslinked by UV irradiation in the presence of diethoxyacetophenone as a photosensitizer, and the micelles with a polyVSA shell were shell‐crosslinked by UV irradiation in the presence of diethoxyacetophenone and 1,6‐hexanedithiol. These crosslinked micelles were pyrolyzed at 600 °C in N₂ to give spherical ceramic particles. The pyrolysis process was examined by thermogravimetry and thermogravimetry/mass spectrometry. The morphologies of the particles were analyzed by atomic force microscopy and transmission electron microscopy. The chemical composition of the pyrolysis products was analyzed by X‐ray fluorescence spectroscopy and Raman scattering spectroscopy. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4696–4707, 2006     

Synthesis of novel crosslinked sulfonated poly(ether sulfone)s using bisazide and their properties for fuel cell application

Novel crosslinked sulfonated poly(ether sulfone)s (PESs) were prepared by thermal irradiation of the allyl-terminated telechelic sulfone polymers using a bisazide. The sulfonated polymers in different comonomer compositions were fully characterized by ¹H NMR, and the crosslinked structure was also verified by FT-IR spectroscopic analyses. Having both the uniform distribution of the hydrophilic conductive sites and controlled hydrophobic nature by minimized crosslinking over the rigid rod poly(ether sulfone) backbone, the crosslinked polymer membrane (PES-60) offered excellent proton conductivity of 0.79 S cm⁻¹ at 100 °C together with hydrolytic and oxidative stability. In addition, only 17% of methanol permeability of the Nafion^® was observed for the crosslinked PES-60.     

Synthesis and characterization of photocrosslinked poly(ε‐caprolactone)s showing shape‐memory properties

Poly(ε‐caprolactone) (PCL) with a pendent coumarin group was prepared by solution polycondensation from 7‐(3,5‐dicarboxyphenyl) carbonylmethoxycoumarin dichloride and α, ω‐dihydroxy terminated poly(ε‐caprolactone) with molecular weights of 1250, 3000, and 10,000 g/mol. These photosensitive polymers underwent a rapid reversible photocrosslinking upon exposure to irradiation with alternating wavelengths (>280/254 nm) without a photoinitiator. The thermal and mechanical properties of the photocrosslinked films were examined by means of differential scanning calorimetry and stress–strain measurements. The crosslinked films exhibited elastic properties above the melting temperature of the PCL segment along with significant decrease in the ultimate tensile strength and Young's modulus. Shape‐memory properties such as strain fixity ratio (R_f) and strain recovery ratio (R_r) were determined by means of a cyclic thermomechanical tensile experiments under varying maximum strains (ε_m = 100, 300, and 500%). The crosslinked ICM/PCL‐3000 and ‐10,000 films exhibited the excellent shape‐memory properties in which both R_f and R_r values were 88–100% for tensile strain of 100–500%; after the deformation, the films recovered their permanent shapes instantaneously. In vitro degradation was performed in a phosphate buffer saline (pH 7.2) at 37 °C with or without the presence of Pseudomonas cepacia lipase. The presence of the pendent coumarin group and the crosslinking of the polymers pronouncedly decreased the degradation rate. The crosslinked biodegradable PCL showing a good shape‐memory property is promising as a new material for biomedical applications. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2422–2433, 2009     

Photodegradation kinetics of poly(para-substituted styrene) in solution

The UV irradiation effects on stability of polystyrene, poly(4-methoxystyrene), poly(4-methylstyrene), poly(α-methylstyrene), poly(4-tert-butylstyrene), poly(4-chlorostyrene), and poly(4-bromostyrene) in dichloromethane, dichloromethane, tetrahydrofuran, and N,N-dimethylformamide solutions were studied in the presence of oxygen at different intervals of irradiation time. The photodegradation was studied at 293 K using fluorescence spectroscopy. Solutions of these polymers were accompanied by quenching of monomer and excimer emissions during the exposure of their solutions to UV light, and by a change in the structure of the fluorescence spectrum. Irradiation of poly(4-methylstyrene) and poly(α-methylstyrene) at excitation wavelength of 265 nm showed an increase of fluorescence intensity of a broad band, at longer wavelength without clear maxima. This may indicate that photodestruction of these polymers by irradiation with light of frequency absorbed by the polymer, may start from a random chain scission, with the possibility of formation of polyene and carbonyl compounds.     

Synthesis and properties of polyacetylenes with salicylideneaniline groups

Acetylenes containing salicylideneaniline groups—N‐salicylidene‐3‐ethynylaniline ( 1 ), N‐(3‐t‐butylsalicylidene)‐3‐ethynylaniline ( 2 ), and N‐(3‐t‐butylsalicylidene)‐4‐ethynylaniline ( 3 )—polymerized smoothly and gave yellow to red polymers in excellent yields when a rhodium catalyst was employed. Polymers with alkyl substituents on the aromatic rings [poly( 2 ) and poly( 3 )] were soluble in CHCl₃, tetrahydrofuran, and so forth, whereas the polymer without alkyl substituents [poly( 1 )] was insoluble in any solvent. N‐(3‐t‐Butylsalicylidene)propargylamine did not provide any polymer. Thermogravimetric analyses of the resultant polymers exhibited good thermal stability (T_o, onset temperature of weight loss > 300 °C). The ultraviolet–visible spectra of the polymers showed absorption maxima and cutoff wavelengths around 360 and 520 nm, respectively. The polymers exhibited largely Stokes‐shifted fluorescence (emission wavelength ? 550 nm) upon photoexcitation at 350 nm, which resulted from the photoinduced intramolecular proton transfer. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2458–2463, 2002     

A simple FTIR spectroscopic method for the determination of the lower critical solution temperature of N‐isopropylacrylamide copolymers and related hydrogels

Linear and crosslinked polymers based on N‐isopropylacrylamide (NIPAAm) exhibit unusual thermal properties. Aqueous solutions of poly(N‐isopropylacrylamide) (PNIPAAm) phase‐separate upon heating above a lower critical solution temperature (LCST), whereas related hydrogels undergo a swelling–shrinking transition at an LCST. A linear copolymer made of NIPAAm/acryloxysuccinimide (98/2 mol/mol) and two hydrogels with different hydrophilicities were prepared. Fourier transform infrared (FTIR) spectroscopy was employed to determine the transition temperature and provide insights into the molecular details of the transition via probing of characteristic bands as a function of temperature. The FTIR spectroscopy method described here allowed the determination of the transition temperature for both the linear and crosslinked polymers. The transition temperatures for PNIPAAm and the gel resulting from the crosslinking with polylysine or N,N′‐methylenebisacrylamide (MBA) were in the same range, 30–35 °C. For the gels, the transition temperature increased with the hydrophilicity of the polymer matrix. The spectral changes observed at the LCST were similar for the free chains and the hydrogels, implying a similar molecular reorganization during the transition. The C H stretching region suggests that the N‐isopropyl groups and the backbone both underwent conformational changes and became more ordered upon heating above the LCST. An analysis of the amide I band suggests that the amide groups of the linear polymer were mainly involved in hydrogen bonding with water molecules below the LCST, the chain being flexible and disordered in a water solution. During the transition, around 20% of these intermolecular hydrogen bonds between the polymer and water were broken and replaced by intramolecular hydrogen bonds. Similar changes were also observed at the LCST of a gel crosslinked with MBA. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 907–915, 2000     

Polymers derived from N‐isopropylacrylamide and azobenzene‐containing acrylamides: Photoresponsive affinity to water

N‐Isopropylacryamide was copolymerized by free‐radical polymerization with N‐[2‐(4‐phenylazophenoxy)ethyl]acrylamide derivatives that were substituted at their 4′‐position with ethoxy, methoxyethoxy, or isopropyl units, or with N‐{2‐[4‐(pyridin‐2‐ylazo)phenoxy]ethyl}acrylamide. The polymers were soluble in cold water and possessed lower critical solution temperatures (LCSTs). The value of the LCST rose a few degrees after UV irradiation and dropped after irradiation with visible light, reversibly, in processes that corresponded to the isomerization of the azobenzene units. The polymers became increasingly hydrophobic after increasing their azobenzene content. The difference of hydrophobicity correlates with the absorption band height at about 400 nm. The structure of the substituent on the azobenzene unit affected both the transition temperature and the hydrophobicity. A change in photoinduced wettability for water was observed to occur on a prepared film at a temperature different from the LCST determined in water. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5200–5214, 2004     

Crosslinking poly[1-(trimethylsilyl)-1-propyne] and its effect on physical stability

Poly[1-(trimethylsilyl)-1-propyne] (PTMSP) has been crosslinked using 3,3′-diazidodiphenylsulfone to improve its solvent resistance and physical stability. This study reports the influence of crosslinking on N₂, O₂ and CH₄ gas permeabilities and fractional free volume (FFV) as a function of time. Crosslinking PTMSP renders it insoluble even in excellent solvents for the uncrosslinked polymer. The gas permeability and FFV of uncrosslinked and crosslinked PTMSP decreased over time, so crosslinking PTMSP does not arrest physical aging. The addition of 10 wt.% polysiloxysilsesquioxanes (POSS) nanoparticles decreased the permeability of PTMSP by 55%, and the permeability and FFV values were stable over time for PTMSP films containing 10 wt.% POSS nanoparticles. The permeability of PTMSP at a given FFV was greater than that of other substituted polyacetylenes, polysulfones or polycarbonates, which is consistent with differences in the arrangement of free volume in these polymers, as probed by positron annihilation lifetime spectroscopy (PALS). Ellipsometry was used to characterize physical aging of thin (400 nm) uncrosslinked and crosslinked PTMSP films supported on silicon wafers. The ellipsometry results showed that crosslinking does not markedly slow physical aging of thin PTMSP films.     

Synthesis of well‐defined macromonomers and comb copolymers from polymers made by atom transfer radical polymerization

Poly(n‐butyl acrylate) macromonomers with predetermined molecular weights (1300 < number‐average molecular weight < 23,000) and low polydispersity indices (<1.2) were synthesized from bromine‐terminated atom transfer radical polymerization polymers via end‐group substitution with acrylic acid and methacrylic acid. These macromonomers, having a high degree of end‐group functionalization (>90%), were radically homopolymerized to obtain comb polymers. A high macromonomer concentration, combined with a low radical flux, was needed to obtain a high conversion of the macromonomers and a reasonable degree of polymerization. By the traditional radical copolymerization of the hydrophobic macromonomers with the hydrophilic monomer N,N‐dimethylaminoethyl methacrylate (DMAEMA), amphiphilic comb copolymers were obtained. The conversions of the macromonomers and comonomer were almost quantitative under optimized reaction conditions. The molecular weights were high (number‐average molecular weight ≈70,000), and the molecular weight distribution was broad (polydispersity index ≈ 3.5). Kinetic measurements showed simultaneous decreases in the macromonomer and DMAEMA concentrations, indicating a relatively homogeneous composition of the comb copolymers over the whole molecular weight range. This was supported by preparative size exclusion chromatography. The copolymerization of poly(n‐butyl acrylate) macromonomers with other hydrophilic monomers such as acrylic acid or N,N‐dimethylacrylamide gave comb copolymers with multimodal molecular weight distributions in size exclusion chromatography and extremely high apparent molecular weights. Dynamic light scattering showed a heterogeneous composition consisting of small (6–9 nm) and large (23–143 nm) particles, probably micelles or other type of aggregates. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3425–3439, 2003