Comb-like Copolymers Research Articles

Alumina interaction with AMPS–MPEG random copolymers III. Effect of PEG segment length on adsorption, electrokinetic and rheological behavior

The effect of different 2-acrylamido-2-methylpropanesulfonic acid sodium salt (AMPS)–methoxypolyethyleneglycol methacrylate (MPEG) comb-like copolymers on the adsorption behavior, electrokinetic and rheological properties of alumina suspensions has been investigated. The change in adsorption isotherms with the content of the two monomers, the medium pH and the ionic strength indicated that the interaction of these copolymers was found to be controlled by both the fraction of ionic groups on the polymer and by the length of the polyethyleneglycol (PEG) segments. Adsorption of the copolymers on alumina particles is accompanied by a shift in the IEP toward acid pH values and may lead to a charge reversal above a certain level. The presence of the PEG segment equally affects the magnitude of the zeta potential by moving the shear plane forward. Addition of the copolymers greatly affects the rheological behavior of the suspension; the viscosity at a defined shear rate decreases and reaches an optimum, which is all the lower as the fraction of the ionic groups is higher. The dispersing effect of the copolymer was controlled by both the ionization level of the copolymer and by the length of the PEG segments.

Compatibilization of PS and PA6 Blends by Means of Poly(oxyalkylene)amine Modified Styrene-Maleic Anhydride Copolymer

The compatibilization effect of SMA-co-M2070-co-DAP comb-like copolymers, SMMD, on immiscible blends of polystyrene (PS) and polyamide-6 (PA6) is examined in terms of phase structure, thermal behavior, dynamic mechanical analysis, and mechanical properties. A series of SMMD copolymers are synthesized and confirmed by the FT-IR analysis. These compatibilizers have different amphiphilic properties depending on the content of hydrophilic poly(oxyethylene) segments (M2070) and the molar ratio of MA/amine. The morphologies of PS/PA6, affected by the increasing amount of SMMD compatibilizer, show a more regular and finer dispersion. The sizes of dispersed particles have no marked changes over the saturation level of compatibilizer. The glass transition temperatures of the blends are between that of PS and PA6, while the added SMMD copolymer is mainly located at the interface. Using these SMMD copolymers, the compatibilized blends show some improvements in mechanical properties, including Izod impact strength and flexural properties. The graft poly(oxyethylene) and amide functionalities in SMMD structures in forming hydrogen bonding with PA6 and, the polystyrene backbone in π–π interaction with PS facilitate the compatibilizing effect.

Nano aggregates of biodegradable amphiphilic poly(hydroxyethyl aspartamide- co-propyl aspartamide) grafted with poly( d, l-lactide)

Amphiphilic graft copolymers composed of poly(hydroxyethyl aspartamide)- co-propyl aspartamide) (PHEA-PA) as the hydrophilic backbone and poly(lactide) (PLA) as the hydrophobic side chain were successfully synthesized by grafting lactide (LTD) onto PHEA-PA. Polysuccinimide (PSI) was firstly synthesized from l-aspartic acid through thermal condensation polymerization method, and then followed by two-step aminolysis processes to form PHEA-PA with different amounts of hydroxyl groups. The hydroxyl groups were then used as initial points to graft PLA onto PHEA-PA backbone via a ring-opening polymerization in the presence of Sn(Oct) 2. The grafting reaction of PLA onto PHEA-PA was confirmed by 1H NMR, FT-IR, and DSC. Micelle-like aggregates were obtained when the amphiphilic comb-like copolymer solution of DMF was added into an excessive amount of water. Strong hydrophobic intramolecular and intermolecular association of PLA chains led to aggregates with hydrophobic microdomains. The dispersion of the self-aggregates of poly(hydroxyethyl aspartamide- co-propyl aspartamide)- g-poly( d, l-lactide) (PHEA-PA- g-PLA) copolymers is stable in aqueous medium. Spherical aggregates of PHEA-PA- g-PLA were observed by transmission electron microscopy (TEM) and scanning electron microscopy (SEM), the diameters were about 100 nm.

Miniemulsion polymerization of styrene using well-defined cationic amphiphilic comblike copolymers as the sole stabilizer

Well-defined, positively charged, amphiphilic copolymers containing long alkyl side chains were used as stabilizers in the miniemulsion polymerization of styrene. The copolymers were prepared by controlled free-radical copolymerization of styrene and vinyl benzyl chloride using either the reversible addition-fragmentation chain transfer method or TEMPO-mediated polymerization. The benzyl chloride moities were modified by two different long alkyl chain tertiary amines (N,N-dimethyldodecyl amine and N,N-dimethylhexadecyl amine) to yield the amphiphilic copolymers with vinylbenzyl dimethyl alkyl ammonium chloride units. Owing to their high structural quality, only a small amount of these copolymers was required to stabilize the latex particles (0.5–2 wt% vs styrene). Moreover, in the absence of any hydrophobic agent, the amphiphilic comblike copolymer preserved the colloidal stability of both the initial liquid miniemulsion and the final latex. Ill-defined, analogous copolymers were synthesized by conventional free-radical polymerization and in comparison, exhibited poor stabilization properties.

Amphiphilic Graft Copolymer in a Selective Solvent: Intramolecular Structures and Conformational Transitions

We present a scaling theory for the equilibrium conformations of amphiphilic comblike (graft-) copolymer in dilute solution. We examine intramolecular self-assembly upon inferior solvent strength for the backbone. We demonstrate that at sufficiently dense grafting the backbone collapses via formation of a pearl necklace of intrachain micelles that are stabilized by steric repulsion between coronas. This behavior is reminiscent to the Rayleigh instability in hydrophobic polyelectrolyte, though occurs in a neutral macromolecule. The equilibrium local structure and the persistence length of comblike copolymer are analyzed as a function of solvent strength. Repulsion between micellar coronas leads to swelling of comblike macromolecule on larger scales and ensures the thermodynamic stability of the solution with respect to phase separation. In the case of sparse grafting we predict formation of not only spherical but also cylindrical intramolecular micelles and lamellar mesophases.

Relaxation Properties of Pressure-sensitive Adhesives upon Withdrawal of Bonding Pressure

ABSTRACT Relaxation properties of pressure-sensitive adhesives (PSA) have been studied with the squeeze-recoil tester used in the regime of parallel-plate dilatometer under conditions imitating the removal of compressive force in the course of adhesive bond formation. The relaxation properties of PSAs are compared with their adhesive behavior measured using the 180-Deg Peel Test. Two classes of PSAs are considered: 1) conventional rubbery adhesives based on the mixtures of styrene-isoprene-styrene (SIS) block copolymer with a tackifier resin and a plasticizer, and butyl rubber plasticized with low-molecular-weight polyisobutylene, and 2) hydrophilic PSAs composed of the blends of high-molecular-weight poly(N-vinyl pyrrolidone) (PVP) with oligomeric polyethylene glycol (PEG). By comparing the adhesive and relaxation behaviors of different PSAs, the relaxation criteria for pressure-sensitive adhesion have been stated. Relaxation behavior of the examined PSAs demonstrates two values of retardation time: the shorter retardation time of 10–70 sec and the longer time of 300–660 sec. These times can be associated, respectively, with small- and large-scale mechanisms of strain recovery. By comparing the relaxation and adhesive properties of PVP-PEG blend (which involves the formation of a hydrogen-bonded network through both terminal hydroxyl groups in PEG short chains) with the properties of covalently crosslinked copolymers of vinyl pyrrolidone (VP) with PEG-diacrylate and comb-like VP copolymers with PEG-monomethacrylate, the contributions of covalent crosslinking and H-bonding network have been characterized.

Stoichiometric polyelectrolyte complexes as comb copolymers

The collapse behavior of a single comblike copolymer chain has been studied by Monte Carlo simulations. It has been supposed that the solvent is good for the side chains but the solvent quality for the backbone chain changes. It has been shown that depending on the structural parameters of the comb copolymer (the lengths of the backbone and side chains, grafting density of the side chains) various thermodynamically stable morphologies of the collapsed backbone chain can be realized. In addition to ordinary spherical globule we have observed elongated structures as well as necklace-like conformations. The proposed model can be used to describe conformational behavior of stoichiometric complexes between block copolymers with a polyelectrolyte short block and oppositely charged linear homopolymers.

Optimization of the synthesis of poly(octadecyl acrylate) by atom transfer radical polymerization and the preparation of all comblike amphiphilic diblock copolymers

AbstractThe atom transfer radical polymerization of octadecyl acrylate (ODA) has been investigated and optimized to produce polymers with predetermined molecular weights and narrow polydispersities (<1.2). The poor solubility of the catalytic system formed with conventional ligands such as the N‐(n‐propyl)‐2‐pyridylmethanimine and 2,2′‐bipyridine with Cu(I)Br in nonpolar reaction conditions gave poor control over molecular weight characteristics in ODA polymerizations. The use of N‐(n‐octyl)‐2‐pyridylmethanimine in combination with Cu(I)Br yielded a more soluble catalyst that improved control over the polymerization. The products from the polymerizations were further improved when an initiator, octadecyl 2‐bromo‐2‐methyl‐propanoate, similar in structure to the monomer, was used. Together, these modifications produced polymerizations that showed true controlled character as well as products with predetermined molecular weights and narrow polydispersities. Diblock copolymers of PODA were prepared with methyl methacrylate (MMA) and olig(oethylene glycol) methyl ether methacrylate (OEGMA). The PODA‐block‐POEGMA copolymers are the first examples of all comblike amphiphilic block copolymers. One of PODA‐block‐POEGMA copolymer samples has been shown to self‐assemble as micelles in a dilute aqueous solution. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1129–1143, 2005

Synthesis by RAFT of Amphiphilic Block and Comblike Cationic Copolymers and Their Use in Emulsion Polymerization for the Electrosteric Stabilization of Latexes

A series of diblock and comblike copolymers based on styrene and 4-vinylbenzyl chloride were synthesized by reversible addition fragmentation transfer (RAFT) using benzyl dithiobenzoate as a control agent. After quaternization of the well-defined hydrophobic precursors with triethylamine, the micellar aggregates, formed by the cationic amphiphilic diblock copolymer when dissolved in water, were investigated by static and dynamic light scattering. The spherical shape of the micelles was established in salted water. Then, the poly(styrene)-b-poly(vinylbenzyltriethylammonium chloride) cationic diblock copolymers were used as a stabilizer for the emulsion polymerization of styrene and appeared to display very good stabilization properties. The ratio between the initial number of micelles and the final number of latex particles was particularly high, as a characteristic of the high mobility of the copolymer chains. Finally, we underlined the strong influence of salt on the nucleation step of the emulsion polym...

Lactone End-Capped Poly(ethylene oxide) as a New Building Block for Biomaterials

This paper reports on the synthesis of a novel poly(ethylene oxide) (PEO) macromonomer, which can be copolymerized with ε-caprolactone (ε-CL) by ring-opening polymerization (ROP). PEO chains end-capped by an ε-caprolactone unit (γPEO·CL) have been synthesized by living anionic ring-opening polymerization of ethylene oxide (EO) initiated by the potassium alkoxide of 1,4-dioxaspiro[4.5]decan-8-ol, followed by derivatization of the acetal into a ketone and the Baeyer−Villiger oxidation of the ketone into a lactone. The end-capping of PEO by ε-CL was assessed by FTIR, MALDI−TOF, and 1H NMR spectroscopy.This type of macromonomer is a precursor of amphiphilic comblike copolymers consisting of a biodegradable hydrophobic backbone of poly-(ε-caprolactone) (PCL) and hydrophilic PEO grafts. Copolymerization of γPEO·CL with ε-CL was successfully initiated by aluminum alkoxide.

A novel comb-like copolymer based polymer electrolyte for Li batteries

Polymer electrolytes, which comprise a novel comb-like copolymer and an alkali metal salt, were successfully prepared and discussed using differential scanning calorimeter, Fourier transform infrared spectroscopy, nuclear magnetic resonance, atom force microscopy, and electrochemical impedance spectroscopy. The novel comb-like copolymer is capable of forming donor:acceptor type bonds with alkali metal ions. The complex system with a mixture of fumed silica or propylene carbonate was studied also. Such electrolytes possess satisfactory ambient temperature ionic conductivity (up to 10 −4 S cm −1) and good mechanical strength. The Vogel–Tamman–Fulcher-like behavior of conductivity implies the coupling of the charge carriers with the segmental motion of the polymer chains.

Synthesis of poly[dimethylsiloxane- block-oligo(ethylene glycol) methyl ether methacrylate]: an amphiphilic copolymer with a comb-like block

AB amphiphilic comb-like block copolymers of poly(oligo[ethylene glycol] methyl ether methacrylate) and polydimethylsiloxane were synthesised with a methodology based on atom transfer radical polymerization (ATRP). The anionic ring opening polymerisation of hexamethylcyclotrisiloxane followed by reaction with 3-(chlorodimethylsilyl) propyl 2-bromo-2-methylpropanoate propyldimethylchlorosilane gave suitable macroinitiators for the ATRP of oligo[ethylene glycol] methyl ether methacrylate. The latter synthetic procedure was optimised by performing a number of syntheses varying the reaction solvent, catalytic complex and the temperature used. Copolymers with relatively high polydispersity indices ( M w/ M n>1.3) could be synthesised at room temperature by employing a Cu(I)Br: N, N, N′, N′, N″-pentamethyldiethylenetriamine complex in n-propanol with Cu(II)Br. The optimum reaction conditions employed a Cu(I)Cl: N-( n-propyl)-2-pyridyl(methanimine) complex with an n-propanol/water mixture or toluene as solvent at 90 °C. This gave block copolymers of the desired molecular weights and polydispersity indices of less than 1.1. The block copolymers were characterised with 1H NMR and 13C NMR spectroscopy and size exclusion chromatography.

Studies on comb-like polymer electrolyte with a nitrile group

The behavior of lithium ions in a comb-like polymer electrolyte with a nitrile group has been characterized by differential scanning calorimeter (DSC), thermogravimetric analysis (TGA), ac impedance, Fourier transform infrared (FTIR) spectroscopy, and 7 Li solid-state NMR measurements. The comb-like copolymer is synthesized by poly(ethylene glycol-methyl ether methacrylate) (PEGMEM) and acrylonitrile (AN). FTIR spectra reveal the interactions of Li + ions with both the ether oxygen of the PEGMEM and the nitrogen atom of the AN segments. 7 Li solid-state NMR spectra demonstrate the interactions of Li + ions with both the ether oxygen of the PEGMEM and the nitrogen atom of the AN segments. Moreover, 7 Li solid-state NMR shows that the lithium ions are preferentially coordinated to the PEGMEM segment. The T g increases for the copolymers doped with LiClO 4. These results indicate the interactions of Li + with both PEGMEM and AN segments form transient cross-links. The dependence of the maximum conductivity on the doping lithium ion concentration was determined. The AN unit in the copolymer improves the dissociation of the lithium salt, and the mechanical strength.

Atomic force microscopy study of comb-like vs. arborescent graft copolymers in thin films

This work deals with the study of comb-like vs. arborescent grafted copolymers made of poly(chloroethyl vinyl ether)- g-polystyrene (PCEVE- g-PS). We describe how the molecular architecture of the branched polymers affects their nanoscale organization in thin films, as observed using atomic force microscopy. The results indicate that modifying the molecular architecture from a ‘generation-zero’ comb-like (PCEVE- g-PS) to a ‘first-generation’ hyperbranched (PCEVE- g-(PS- b-PCEVE- g-PS)) architecture strongly modifies the observed geometrical parameters of the molecules, in good agreement with the expected evolution of the molecular dimensions and the corresponding data obtained in solution. The surface organization of the (PCEVE- g-PS) copolymer molecules is also strongly conditioned by the interplay between the molecule–substrate interactions and the molecule–molecule interactions, leading to different possible orientations of the lateral branches with respect to the surface and thus to different final morphologies.

Conductivity, DSC, and solid-state NMR studies of comb-like polymer electrolyte with a chelating functional group

The behavior of lithium ions in a comb-like polymer electrolyte with a chelating functional group has been characterized by differential scanning calorimetry (DSC), AC impedance, 13C and 7Li solid-state nuclear magnetic resonance (NMR) measurements. The comb-like copolymer is synthesized by poly(ethylene glycol) methyl ether methacrylate (PEGMEM) and (2-methylacrylic acid 3-(bis-carboxymethylamino)-2-hydroxy-propyl ester) (GMA–IDA). 7Li solid-state NMR spectra demonstrate the interactions of Li + ions with both the ether oxygen of the PEGMEM and the nitrogen atom of the GMA–IDA segments. Moreover, 7Li solid-state NMR shows that the lithium ions are preferentially coordinated to the GMA–IDA segment. Moreover, the 13C solid-state NMR spectra for the carbons attached to the ether oxygen atoms exhibited significant line broadening and a slight upfield chemical shift and short T CH when the dopant was added to the polymer. These findings indicate coordination between the Li cation and the ether oxygens in the PEG segment. T g increases for the copolymers doped with LiClO 4. These results indicate the interactions of Li + with both PEGMEM and GMA–IDA segments form transient cross-links. The Vogel–Tamman–Fulcher (VTF)-like behavior of conductivity implies the coupling of the charge carriers with the segmental motion of the polymer chains. The dependence of the maximum conductivity on the composition of the copolymers and the doping lithium ion concentration was determined. The GMA–IDA unit in the copolymer improves the dissociation of the lithium salt, the mechanical strength and the conductivity.

Synthesis and characterization of new alternating, amphiphilic, comblike copolymers of poly(ethylene oxide) macromonomer andN-phenylmaleimide

A surface-active p-vinyl benzyloxy--hydroxy-poly(ethylene oxide) mac- romonomer containing 22 pendant structural units of ethylene oxide (St-PEO22) was synthesized with an initiation method. Because of its solubility in a large variety of solvents, the free-radical copolymerization with electron-acceptor N-phenylmaleimide (NPMI) was performed at 60 °C in benzene and tetrahydrofuran (THF) as isotropic media and in a water-THF mixture or water as a heterogeneous medium. Oil-soluble 2,2-azobisisobutyronitrile and water-soluble 4,4-azobis(4-cyanovaleric acid) were used as the initiators at fixed concentrations. Two different St-PEO22/NPMI comonomer ratios (1/1 and 3/7) at a fixed total comonomer concentration in the polymerization system were used. The structures, compositions, and microstructure peculiarities of the obtained alternating, amphiphilic, comblike copolymers were determined by NMR analysis. For the copolymers synthesized in hydrophilic media, differential scanning calorimetry showed, near the endothermic peak attributed to the melting of the poly- (ethylene oxide) side chains, the presence of a second peak due to the partially ordered phase that could exist between the crystalline state and the isotropic melt. Also, the thermal stability of the obtained copolymers was studied with thermogravimetric analysis. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 479 - 492, 2005

Influence of azobenzene concentration on the dielectric behavior of amorphous comb-like copolymers with photochromic side groups

Dielectric spectroscopy in the frequency range from 10 −2 to 10 6 Hz and in the temperature range from 190 to 440 K is employed to study the effect of azobenzene concentration on the dielectric relaxation processes of an amorphous comb-like copolymethacrylate. Four concentrations ( x=29, 45.5, 54, and 74.5 mol%) of photochromic group 4-amino-azobenzene were investigated, where as comonomer a methacrylate unit having a derivative of benzanilide in the side group is used. Two prominent processes, the β-relaxation at low temperatures which is related to rotational fluctuations of the mesogenic unit around its long axes and the dynamic glass transition (α-relaxation, segmental dynamics) at higher temperatures are observed for all azobenzene concentrations. In addition in between the α- and the β-relaxation a β′-process is observed for the polymers with the two lowest azobenzene concentrations, which seems to be related to the azobenzene unit. The dependence of the dielectric strength and the relaxation rate of the relaxation processes on the azobenzene concentration is discussed and interpreted in a simple phenomenological model, where also data obtained by semi empirical quantum chemical calculations are used.

Surface Characteristics of Comblike Copolymers from Hexadecylacrylamide and Acrylic Acid at the Air/Water Interface

The interfacial organization characteristics of comblike copolymers from hexadecylacrylamide and acrylic acid at the air/water interface have been investigated using a Langmuir film balance at pH 6.5 and 10.0. The homopolymer and the copolymers (CHXP1, CHXP2) exhibit A o values of about 0.26 nm 2 /molecule with a π m a x value of about 40 mN/m. The small differences in the surface characteristics of the copolymers suggest that the hexadecylacrylamide polymers undergo little changes in packing characteristics with the introduction of acrylic acid even up to 15 mol %. However, the copolymer consisting of 22 mol % acrylic acid tends to form a more expanded film, as is suggested from the comparatively higher A 0 (0.28 nm 2 / molecule) and compressibility coefficient, k of 1.07 x 10 - 2 m/mN at π = 25 mN/m. The high surface concentration (Γ), 2.0-2.2 mg/m 2 , and π m a x of 40 mN/m of the investigated polymers are in support of the packing of the hexadecyl side chain at the interface. The results of the π-A isotherm and hysteresis experiments at pH 10.0 suggest that an introduction of an optimum level of 15 mol % acrylic acid in the copolymer imparts stabilization of the hexadecylacrylamide polymer film at the interface. The presence of 22 mol % acrylic acid shifts the amphiphilic balance of the copolymer to a more hydrophilic structure and promotes the desorption of the film into an aqueous subphase, especially under alkaline conditions leading to instability.

The environment of lithium ions and conductivity of comb-like polymer electrolyte with a chelating functional group

The behavior of lithium ions in a comb-like polymer electrolyte with a chelating functional group have been characterized by differential scanning calorimeter (DSC), dynamic mechanical analysis (DMA), Fourier transform infrared (FTIR) spectroscopy, ac impedance and 7Li solid-state NMR measurements. The comb-like copolymer is synthesized by poly(ethylene glycol-methyl ether methacrylate) (PEGMEM) and (2-methylacrylic acid 3-(bis-carboxymethylamino) -2-hydroxy-propyl ester) (GMA-IDA). FTIR and 7Li solid-state NMR spectra demonstrate the interactions of Li + ions with both the ether oxygen of the PEGMEM and the nitrogen atom of the GMA-IDA segments. Moreover, 7Li solid-state NMR shows that the lithium ions are preferentially coordinated to the GMA-IDA segment. The T g increases for the copolymers doped with LiClO 4. These results indicate the interactions of Li + with both PEGMEM and GMA-IDA segments form transient cross-links. The Vogel–Tamman–Fulcher (VTF)-like behavior of conductivity implies the coupling of the charge carriers with the segmental motion of the polymer chains. The dependence of the maximum conductivity on the composition of the copolymers and the doping lithium ion concentration was determined. The GMA-IDA unit in the copolymer improves the dissociation of the lithium salt, the mechanical strength and the conductivity.

Polymer functionalized submicrometric emulsions as potential synthetic DNA vectors

Triglyceride-based emulsions were first prepared by a solvent displacement procedure which was modified to achieve their functionalization by surface deposition of various amphiphilic comb-like copolymers. These emulsions have been characterized as regards to hydrodynamic particle size and surface charges using dynamic light scattering and electrophoretic mobility measurements. The adsorption isotherms of a polydT15 oligonucleotide and a model plasmid showed that the process was dependent on the nature of the interfaces, the affinity for the nucleic acid increasing with more cationic charges, together with improved accessibility. The binding process was found to proceed according to two regimes: one at low nucleic acid coverage, independent of the initial plasmid concentration, and the second one at high coverage, which was nucleic-acid-concentration dependent. This behavior was considered to occur because of the development of repulsive interactions upon increasing the amount of immobilized nucleic acid. The complexation of plasmid complexed at the interface was finally investigated using the ethidium bromide displacement technique. The level of compaction of plasmid complexed onto the functionalized emulsions was lower than that obtained with the parent free polymer.