Comb-like Polymers Research Articles

Wettability of the morphologically and compositionally varied surfaces prepared from blends of well ordered comb-like polymer and polystyrene

Phase-separated surfaces of blends of polystyrene (PS) and well ordered comb-like polymer, poly[(oxy(decylsulfonylmethyl)ethylene)] (CH 3-10SE), were prepared by spin casting polymer mixtures. Various surface morphologies, such as holes, islands, connected islands and pillars, were prepared by changing the blend compositions. Due to the influence of the CH 3-10SE domain with a well ordered molecular conformation, a very low energy surface (≈22 mN/m) was created, which is close to the value of the pure polymer (≈20 mN/m), even when the blends contained only 20 wt.% of the pure polymer. Furthermore, by selective etching the PS domain in the blend surfaces, the advancing contact angles of water and n-hexadecane were highly increased from 113.5° and 43.2° for the pure CH 3-10SE surface to 133.3° and 67.2° for the CH 3-10SE structural surfaces with holes prepared using the solvent etching method, respectively. The result of the water advancing contact angles measured on the samples immersed in water over 20 days showed that the film stability of CH 3-10SE could be improved considerably by even adding small amounts of PS.

Synthesis and phase behaviour of new cholesteric monomers and side chain smectic polymers based on cholesterol

The synthesis of five new cholesteryl-based monomers (M-1−M-5) and the corresponding smectic comb-like polymers containing cholesteryl groups (P-1−P-5) is presented. The chemical structures were characterised by FT-IR, 1H NMR and elemental analyses. The specific optical rotations were evaluated with a polarimeter. The phase behaviour was investigated by polarising optical microscopy, differential scanning calorimetry, thermogravimetric analysis, and X-ray diffraction. The specific optical rotation values of these monomers and polymers with the same number of phenyl rings and terminal groups were nearly equal; however, they decreased with increasing the aryl numbers in the mesogenic core. The monomers M-1−M-5 showed oily streak and focal conic optical textures, or finger print textures characteristic of the chiral nematic phase. The polymers P-1−P-5 showed the smectic A phase. The melting, clearing, and glass transition temperatures increased, and the mesophase temperature ranges widened with increasing the aryl number in the mesogenic core. However, although the molecular structures of M-4 and M-5 were similar to those of M-3, namely their mesogenic cores contained three phenyl rings, their phase behaviour differed considerably, and T m and T i of M-4 and M-5 were less than those of M-3. In addition, M-4 and M-5 showed a clear glass transition similar to the polymer. Furthermore, the ester linkage bond and aryl arrangement in the mesogenic core also affected the phase behaviour.

Degradable, pH-sensitive, membrane-destabilizing, comb-like polymers for intracellular delivery of nucleic acids

This report describes the design and synthesis of a new series of degradable, pH-sensitive, membrane-destabilizing, comb-like polymers that can enhance the intracellular delivery of therapeutic nucleic acids. These comb-like polymers are based on a diblock polymer backbone where the first block is a copolymer of pH-sensitive ethyl acrylic acid (EAA) monomers and hydrophobic butyl methacrylate (BMA) or hexyl methacrylate monomers. The second block is a homopolymer of N-acryloxy succinimide (NASI) or ß-benzyl l-aspartate N-carboxy-anhydride (BLA-NCA) monomers, which are functionalized to allow controlled grafting of hydrophobic HMA and cationic trimethyl aminoethyl methacrylate (TMAEMA) copolymers via acid-labile hydrazone linkages. These comb-like polymers displayed high hemolytic activity in acidic solutions, which increased with the increase in polymer concentration. All comb-like polymers degraded into small fragments upon incubation in an acidic solution (pH 5.8) due to hydrolysis of the hydrazone linkages connecting the hydrophobic/cationic grafts to the polymer backbone. Comb-like polymers successfully complexed anti-GAPDH siRNA molecules into serum- and nuclease-stable particles, which successfully silenced GAPDH expression at both the mRNA and protein levels. These results collectively indicate the potential of these new comb-like polymers to serve as vehicles for effective intracellular delivery of therapeutic nucleic acids.

Elastic behavior of comb-like polymer chains

Three-dimensional Monte Carlo simulations of comb-like polymer chains with various backbone lengths N b, arm lengths N a and arm densities m are carried out to study the elastic behavior of comb-like polymer chains. The radius of gyration, the shape factors and bond length in different cases during elastic process are calculated, and it is found that the comb-like polymer molecules with longer backbone or shorter arm are more close to linear chains. But the arm density m affects the chain conformation non-monotonously. Some thermodynamic properties are also studied. Average Helmholtz free energy and elastic force f all increase with elongation ratio λ for all chains.

Local-field anisotropy of a light wave in quasi-two-dimensional soft-matter objects

Experimental values of the Lorentz tensor components Lj for uniaxial quasi-two dimensional “soft matter” objects on substrates (bilayer lipid membranes, multilayer Langmuir films, smectics A, hexatic smectics B, submicron films of discotics Colhd, micron anisotropic films of liquid-crystal comblike polymers and macromolecular polymers, submicron films of conjugated conductive polymers), freely suspended submicron films of smectics A, and uniaxially stretched micron films of conjugated conductive polymers have been determined using dispersion of refractive indices in the visible range. The dependences of the components Lj on the type of orientation (axial, planar) of uniaxial molecules (structural units of the film) with respect to the optical axis of the film, the film thickness, the substrate type, the chemical structure of molecules, and their long-range orientational order are established. It is revealed that the smectic A-hexatic B phase transition and two-dimensional crystallization of the smectic layer lead to changes in the components Lj due to the change in the orientational ordering of molecules as a result of the relation between the orientational and hexatic order parameters. All the above objects are characterized by isotropization of the Lorentz tensor L and the local-field tensor f with a simultaneous decrease in the birefringence of the sample and in the anisotropy of the molecular polarizability due to the change in the electronic structure of molecules. The correction for the anisotropy of the local-field tensor f to the orientational order parameter or the anisotropy of the molecular polarizability increases. The existing model approaches to calculating the components Lj for the objects under consideration are compared with the experimental data.

Inhibition of bacterial adhesion on well ordered comb-like polymer surfaces

The surfaces of comb-like poly(oxyethylene) derivatives with n-alkylsulfonyl side groups were more effective at reducing Pseudomonas aeruginosa adhesion than the surfaces of common materials such as polystyrene, poly(methyl methacrylate), poly(dimethylsiloxane), fluorinated polyacrylate, and glass. When the comb-like poly(oxyethylene) was mixed with polystyrene and poly(methyl methacrylate), the topology and roughness of the surfaces varied according to the mixture compositions. However the surface energies of the mixtures were close to that of the comb-like poly(oxyethylene) in the range of 21–23 mN/m and bacterial adhesion resistances of the mixture surfaces were also comparable to that of the pure comb-like poly(oxyethylene) surface.

Synthesis, structure and mesomorphism of new cholesteric monomers and smectic comblike polymers

Seven new cholesteric monomers ( M-1− M-7) and the corresponding smectic comblike polymers containing cholesteryl groups ( P-1− P-7) were synthesized. The chemical structures and purity were characterized by FT-IR, 1H NMR, and elemental analyses. The specific optical rotations were evaluated with a polarimeter. The mesomorphism was investigated by polarizing optical microscopy, differential scanning calorimetry, thermogravimetric analysis, and X-ray diffraction. The specific optical rotation values of these monomers and polymers with the same numbers of phenyl ring and terminal groups were nearly equal, however, they decreased with increasing the aryl numbers in the mesogenic core. M-1− M-7 showed oily streak texture and focal conic texture, or fingerprint texture, or spiral texture of cholesteric phase. P-1− P-7 showed the smectic A phase. The melting, clearing, and glass transition temperatures increased, and the mesophase temperature ranges widened with increasing the aryl number in the mesogenic core. Surprisingly, although the molecular structures of M-6 and M-7 were similar to those of M-4, namely the mesogenic cores contained three phenyl rings, their phase behavior had a considerable difference, and T m and T i of M-6 and M-7 were less than those of M-4. In addition, M-6 and M-7 also showed an obvious glass transition. TGA showed that all the polymers had good thermal stabilities.

Synthesis and properties of gel polymer electrolyte membranes based on novel comb-like methyl methacrylate copolymers

Based on the principle of molecular design, three comb-like methyl methacrylate copolymer matrixes for gel polymer electrolyte (GPE) were designed and synthesized by reacting methyl methacrylate-maleic anhydride copolymer (P(MMA-MAh)) with poly(ethylene glycol) monomethyl ether (PEGME) of different molecular weight (350, 600, and 750) respectively. The structures of comb-like polymers were characterized by Fourier transform infrared (FTIR) and 1H-nuclear magnetic resonance ( 1H NMR), and their thermal properties were investigated with differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The membranes of P(MMA-MAh) copolymer and comb-like copolymer based polymer electrolytes, plasticized with propylene carbonate (PC) and LiClO 4 as salt, have been prepared by solution casting technique respectively. And AC impedance was used to characterize the ion conductivity of GPE systems. Compared with P(MMA-MAh) copolymer, introducing the flexible ether chain segments can reduce the resistance of ion transport in polymer matrix and improve the mobility of electroactive ions in the GPE systems. With the increase in side chain length of copolymers, ionic conductivity of GPEs is improved dramatically. The highest conductivity observed in MMA/MAh-g-PEGME600 GPE system (matrix content: 45 wt%) is 1.22 × 10 −3 S/cm at 60 °C. And temperature dependence of GPE membranes could be described by Vogel–Tamman–Fulcher (VTF) behavior. TGA curves showed that these gel polymer electrolyte membranes possessed favorable thermal stability for lithium ion battery use.

Comb-like poly(4-vilylpyridinium) salts with dodecylsulfate, sodium bis(2-ethylhexyl) sulfosuccinate and bromide counter ions. Small-angle X-ray scattering and dynamic light scattering study

Poly(4-vinylpyridine) derivatives alkylated with dimethylsulfate, octylbromide and dodecylbromide were synthesized. Bromide anions in the polymer salts were substituted with octylsulfate, dodecylsulfate or bis(2-ethylhexyl)sulfosuccinate (AOT) anions using ion-exchange reactions. The small-angle X-ray scattering (SAXS) studies of the structure of the comb-like polysalts demonstrated their highly-ordered structure. Loading the comb-like polycation with the surfactant anions leads to additional ordering of the polysalts structure. In the case of large AOT anions the transition from lamella to hexagonal structure is observed. Polyelectrolyte – surfactant complexes (PEC) of poly(4-vinyl-1-methylpyridinium) cation with octylsulfate and dodecylsulfate counter ions demonstrate a higher degree of order than the comb-like polymers having a similar chemical structure. The SAXS studies were complemented by dynamic light scattering study of the solutions of the polymers in chloroform. In the solution the comb-like polymers and their complexes with linear surfactants have coil conformations with the size of the coils close to that of the original poly-4-vinylpyridine. The conformations of PECs with octylsulfate and dodecylsulfate counter ions are more unfolded than those of the corresponding comb-like polymers.

Comb-like polymer blends of poly(oxyethylene)s with CH 3-terminated and CF 3-terminated alkylsulfonylmethyl side chains: Effect of terminal CF 3 moiety on the surface properties of the blends

The surface properties of comb-like polymer blends of poly(oxyethylene)s having CH 3-terminated and CF 3-terminated alkylsulfonylmethyl side chains were studied. These side chains were found to be well oriented on the surface of the blends, while being phase separated, forming various surface morphologies composed of holes, islands, or connected islands, because of their immiscibility resulting from their different polarities. The domain size of each polymer on the blend surface was found to be almost linearly proportional to the bulk compositions of the mixture, and the CF 3-terminated alkylsulfonylmethyl side chain domains were found to be located in the lower region of the surface. The polar CF 3-terminal groups in the lower regions were deemed to control the surface properties, because the contact angles and stick–slip behaviors of the blends containing more than 40 mol% of poly(oxyethylene) with CF 3-terminated side chains were almost identical.

Thermoanalytical Studies on the Polymorphism of Long-chain Vinyl Compounds and Comb-like Polymers

Thermoanalytical Studies on the Polymorphism of Long-chain Vinyl Compounds and Comb-like Polymers

Synthesis and thermal behavior of telechelic poly(butadiene)diols with azobenzene-based liquid-crystalline units in side chains

Mesogenic thiols with azobenzene as a rigid part and with various substituent (H-, methoxy-, butoxy- or octyloxy-) in para-position of azobenzene ring were synthesized by multi-step syntheses. The thiols were grafted onto double bonds of telechelic poly(butadiene)diol (M n ~ 2,400, functionality f n = 2, 60 mol.% of 1,2-butadiene units) via radical addition in the presence of 2,2′-azobis(2-methylpropionitrile) (AIBN). Initial mole ratio of thiol/double bonds varied in the range of 0.2–1.0. Influence of the azobenzene substituent on the extent of modification reaction was estimated using elemental analysis, size-exclusion chromatography and 1H NMR spectroscopy. The substituent on mesogen plays also an important role in thermal behavior of both the thiols and the obtained comb-like polymers, as determined by differential scanning calorimetry and polarizing optical microscopy.

Role of grafted chains for the in situ formation of Ag nanoparticles within poly(epichlorohydrin)- g-polymethacrylate films

Two kinds of amphiphilic comb-like copolymer, i.e., poly(epichlorohydrine)- g-poly(methyl methacrylate) (PECH- g-PMMA) and poly(epichlorohydrine)- g-poly(butyl methacrylate) (PECH- g-PBMA) were synthesized via atom transfer radical polymerization (ATRP) using directly initiating the chlorine atoms of PECH macroinitiator. The amphiphilic comb-like copolymers were used as a template film for the in situ growth of silver nanoparticles from AgCF 3SO 3 precursor using NaBH 4. UV–visible spectroscopy and transmission electron microscopy (TEM) images indicated that (1) Ag nanoparticles were selectively confined in the comb-like polymer films persisting microphase-separated morphology and (2) Ag nanoparticles (4–7 nm) formed in PECH- g-PBMA were smaller than those in PECH- g-PMMA (6–11 nm). This represents that the longer hydrophobic side chains in a comb-like copolymer is more effective in controlling the formation of metal nanoparticles.

Synthesis and Characterization of a New Class of Cationic Protein Polymers for Multivalent Display and Biomaterial Applications

Monodisperse protein polymers engineered by biosynthetic techniques are well suited to serve as a basis for creating comb-like polymer architectures for biomaterial applications. We have developed a new class of linear, cationic, random-coil protein polymers designed to act as scaffolds for multivalent display. These polymers contain evenly spaced lysine residues that allow for chemical or enzymatic conjugation of pendant functional groups. Circular dichroism spectroscopy and turbidity experiments have confirmed that these proteins have a random coil structure and are soluble up to at least 65 degrees C. Cell viability assays suggest these constructs are nontoxic in solution up to a concentration of 100 microM. We have successfully attached a small bioactive peptide, a peptoid-peptide hybrid, a poly(ethylene glycol) polymer, and a fluorophore to the protein polymers by chemical or enzymatic coupling, demonstrating their suitability to serve as multivalent scaffolds in solutions or as gels.

Calcite Morphology and Aggregation in the Presence of Comb-like Polymers Adsorbed on Cement Particles

Comb-like polymers have an important application in cement industries, where they are referred to as polymeric admixtures/superplasticizers. They are used to increase the workability of fresh cementitious mixtures as well as to improve the strength and durability of the hardened state. So far, the interaction of polymer/Portland-limestone cement particles has been poorly investigated. This paper describes the overgrowth of calcite on Portland-limestone cement particles, a mixture of ground clinker and calcite, in the presence of comb-like polymers. The morphological and aggregational variation of overgrown calcite crystals is used as a model to evaluate the interaction occurring between cement particles and polymeric admixtures. Rhombohedral, spherulitic, microtrumpet, or fibrous calcite crystals were observed as a function of the kind of cement particles and comb-like polymers used. These results suggest that comb-like polymers may assume diverse conformations when associated with the different particles that constitute Portland-limestone cement.

Preparation and Non-Invasive In-Vivo Imaging of Anti-Adhesion Barriers with Fluorescent Polymeric Marks

Comb-like PEMLn polymers with pendent PEG-PLLA side chains were synthesized as tissue anti-adhesion barriers. The comb-like structure improved the flexibility of the films. Fluorescent polymer-biocompatible polymer guest-host materials were printed on the films as marking dots. Without sacrificing rats on different days after surgery, degradation behaviors of the marked films can be investigated non-invasively in the in-vivo imaging system (IVIS) by monitoring the location of fluorescent signals. Degradation properties of PEML1/G26L35 films were adjusted by incorporating G26L35 oligomers. PEML1 and PEML1/G26L35 films were very effective in preventing post-surgical tissue-adhesions. Degradation behaviors of various films observed in the animal study were consistent with those investigated by the in-vivo imaging method. Fluorescent polymer/biocompatible polymer blends were promising candidates for in-vivo imaging applications.

Stimuli-responsive copolymers of n-isopropyl acrylamide with enhanced longevity in water for micro- and nanofluidics, drug delivery and non-woven applications

The aim of this study is in radical copolymerization of stimuli-responsive poly(methyl methacrylate/N-isopropyl acrylamide) [P(MMA/NIPAM)] and poly(methyl methacrylate/N-isopropyl acrylamide/acrylic acid) [P(MMA/NIPAM/AAc)] copolymers with an enhanced longevity in aqueous surroundings. [P(MMA/NIPAM)] copolymers are shown to be thermo-responsive, whereas [P(MMA/NIPAM/AAc)] copolymers are shown to be pH-responsive. Such copolymers of NIPAM and MMA or NIPAM, MMA and AAc are synthesized as random polymers, where all monomer units are randomly arranged along the polymer backbone (or as comb-like polymers) and connected by covalent bonds. In distinction from the traditional copolymers based on NIPAM, the copolymers synthesized in the present work possess covalent bonds connecting all the monomers, which enhances their stability in water. In addition, these novel copolymers have sufficiently high molecular weight, which allows for their processing viaelectrospinning. Non-woven materials of these novel copoloymers are of interest for such applications as micro- and nanofluidics, disposable wipers, drug carriers, and tissue engineering.

Investigation of the dewetting inhibition mechanism of thin polymer films

The mechanism of inhibition of polymer film dewetting is investigated by adding a star comb-like polymer, four-arm P(S-ran-VB-g-PMMA), to PS film and PMMA film on different substrates. It is found that the mechanism of inhibition of polymer film dewetting is kinetic in nature, and is related to the miscibility between the additional compound and the polymer film. On addition to the miscible system [four-arm P(S-ran-VB-g-PMMA) and PMMA], the star comb-like polymers can increase the resistant force of dewetting with hole growth and inhibit the dewetting process of the thin polymer film by enrichment in the rim. To the immiscible system [four-arm P(S-ran-VB-g-PMMA) and PS], firstly the four-arm P(S-ran-VB-g-PMMA) enriches the solid substrate and forms nanodroplets in the process of spin-coating, and then PS film dewets on these nanodroplets; however, the star comb-like polymer can inhibit the dewetting of the polymer film only when the contact angle θ of the polymer on the additional four-arm P(S-ran-VB-g-PMMA) is smaller than that of the polymer on the substrate.

Small Angle Neutron Scattering Study of Conformation of Oligo(ethylene glycol)-Grafted Polystyrene in Dilute Solutions: Effect of the Backbone Length

The conformation and clusterization of comblike polymers of polystyrene densely grafted with oligo(ethylene glycol) (OEG) side chains in 1.0 wt % solutions of D2O, toluene-d8, and methanol-d4 was investigated as a function of the degree of polymerization (DP) of the backbone by small angle neutron scattering (SANS). Each side chain had four EG repeat units, and the DP of the polystyrene backbone varied from 8 to 85. The global conformation of the polymers in toluene and methanol was shown to assume ellipsoidal, rigid cylindrical, or wormlike morphologies with increasing DP of the polystyrene backbone. At the same time, in D2O, the polymer conformation was described by the form factor of rigid cylinders. The second viral coefficient A2 was measured for the polymer with a DP of 85 in all three solvents, and the solvent quality of toluene, methanol, and D2O was identified to be good, marginal, and poor, respectively, for this polymer. Because of a poor solvent quality, the PS backbone (DP = 85) is partially collapsed in D2O, whereas it is moderately expanded in toluene and methanol. Polymers with a DP of 8 were found to form clusters in all three solvents, with the characteristic size between 100 and 200 Å and a fractal dimension of 2. With the increase in the DP, the clusters diminished in D2O and completely disappeared in toluene and methanol. This observation suggests that the clusterization of these short side-chain polymers is caused by end-group and hydrogen bonding interactions between different chains.

Light-Induced Director Reorientation in Nematic Liquid Crystals Doped with Azobenzene-Containing Macromolecules of Different Architecture

The results of the studies of the orientational optical nonlinearity of a nematic host doped with high-molar-mass compounds of different molecular architecture such as a comb-like polymer and a dendrimer containing azobenzene chromophores are presented. The nonlinearity induced by these compounds was found to be higher than that induced by the low-molar-mass dyes similar in structure to the light-absorbing constituents of the polymer and dendrimer. Possible reasons for the nonlinearity enhancement for macromolecular dopants are discussed.