A novel fluorine‐containing graft copolymer bearing perfluorocyclobutyl aryl ether‐based backbone and poly(methyl methacrylate) side chains

A series of novel graft copolymers consisting of perfluorocyclobutyl aryl ether‐based backbone and poly(methyl methacrylate) side chains were synthesized by the combination of thermal [2π + 2π] step‐growth cycloaddition polymerization of aryl bistrifluorovinyl ether monomer and atom transfer radical polymerization (ATRP) of methyl methacrylate. A new aryl bistrifluorovinyl ether monomer, 2‐methyl‐1,4‐bistrifluorovinyloxybenzene, was first synthesized in two steps from commercially available reagents, and this monomer was homopolymerized in diphenyl ether to provide the corresponding perfluorocyclobutyl aryl ether‐based homopolymer with methoxyl end groups. The fluoropolymer was then converted to ATRP macroinitiator by the monobromination of the pendant methyls with N‐bromosuccinimide and benzoyl peroxide. The grafting‐from strategy was finally used to obtain the novel poly(2‐methyl‐1,4‐bistrifluorovinyloxybenzene)‐g‐poly(methyl methacrylate) graft copolymers with relatively narrow molecular weight distributions (M_w/M_n ≤ 1.46) via ATRP of methyl methacrylate at 50 °C in anisole initiated by the Br‐containing macroinitiator using CuBr/dHbpy as catalytic system. These fluorine‐containing graft copolymers can dissolve in most organic solvents. This is the first example of the graft copolymer possessing perfluorocyclobutyl aryl ether‐based backbone. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

pH-thermosensitive behavior of N,N-dimethylaminoethyl methacrylate (Co)polymers with N-vinylcaprolactam

The effect of acidity of a medium on the phase separation temperature and the intensity of light scattering for dispersions produced by heating of aqueous solutions of N,N-dimethylaminoethyl methacrylate, N-vinylcaprolactam, and their copolymers has been studied. It has been demonstrated that the phase separation temperature and the turbidity of polyvinylcaprolactam (and vinylcaprolactam-enriched copolymers) solutions are pH-independent. Poly(N,N-dimethylaminoethyl methacrylate) (and N,N-dimethylaminoethyl methacrylateenriched copolymers) exhibits temperature sensitivity only in the alkaline region, and the phase separation temperature and turbidity versus pH plots are described by curves with maxima. The addition of sodium dodecyl sulfate to polymer solutions in the general case causes an increase in the phase separation temperature. However, if positive charges occur on macromolecules (in initial solutions of poly(N,N-dimethylaminoethyl methacrylate) or acidified solutions of polyvinylcaprolactam), the increase in the phase separation temperature is preceded by its decrease owing to the electrostatic interaction of surfactant anions with cationic centers. As acid is introduced into the H₂O-sodium dodecyl sulfate-polyvinylcaprolactam ternary system, the phase separation temperature of the polyvinylcaprolactam-dodecyl sulfate complex is decreased.     

Well‐defined amphiphilic graft copolymer consisting of hydrophilic poly(acrylic acid) backbone and hydrophobic poly(vinyl acetate) side chains

A series of well‐defined amphiphilic graft copolymers containing hydrophilic poly(acrylic acid) (PAA) backbone and hydrophobic poly(vinyl acetate) (PVAc) side chains were synthesized via sequential reversible addition‐fragmentation chain transfer (RAFT) polymerization followed by selective hydrolysis of poly(tert‐butyl acrylate) backbone. A new Br‐containing acrylate monomer, tert‐butyl 2‐((2‐bromopropanoyloxy)methyl) acrylate, was first prepared, which can be polymerized via RAFT in a controlled way to obtain a well‐defined homopolymer with narrow molecular weight distribution (M_w/M_n = 1.08). This homopolymer was transformed into xanthate‐functionalized macromolecular chain transfer agent by reacting with o‐ethyl xanthic acid potassium salt. Grafting‐from strategy was employed to synthesize PtBA‐g‐PVAc well‐defined graft copolymers with narrow molecular weight distributions (M_w/M_n < 1.40) via RAFT of vinyl acetate using macromolecular chain transfer agent. The final PAA‐g‐PVAc amphiphilic graft copolymers were obtained by selective acidic hydrolysis of PtBA backbone in acidic environment without affecting the side chains. The critical micelle concentrations in aqueous media were determined by fluorescence probe technique. The micelle morphologies were found to be spheres. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6032–6043, 2009     

A successive route to amphiphilic graft copolymers with a hydrophilic poly(3‐hydroxypropyl methacrylate) backbone and hydrophobic polystyrene side chains

A successive method for preparing novel amphiphilic graft copolymers with a hydrophilic backbone and hydrophobic side chains was developed. An anionic copolymerization of two bifunctional monomers, namely, allyl methacrylate (AMA) and a small amount of glycidyl methacrylate (GMA), was carried out in tetrahydrofuran (THF) with 1,1‐diphenylhexyllithium (DPHL) as the initiator in the presence of LiCl ([LiCl]/[DPHL]₀ = 2), at −50 °C. The copolymer poly(AMA‐co‐GMA) thus obtained possessed a controlled molecular weight and a narrow molecular weight distribution (M_w /M_n = 1.08–1.17). Without termination and polymer separation, a coupling reaction between the epoxy groups of this copolymer and anionic living polystyrene [poly(St)] at −40 °C generated a graft copolymer with a poly(AMA‐co‐GMA) backbone and poly(St) side chains. This graft copolymer was free of its precursors, and its molecular weight as well as its composition could be well controlled. To the completed coupling reaction solution, a THF solution of 9‐borabicyclo[3.3.1]nonane was added, and this was followed by the addition of sodium hydroxide and hydrogen peroxide. This hydroboration changed the AMA units of the backbone to 3‐hydroxypropyl methacrylate, and an amphiphilic graft copolymer with a hydrophilic poly(3‐hydroxypropyl methacrylate) backbone and hydrophobic poly(St) side chains was obtained. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1195–1202, 2000     

Synthesis, rapid responsive thickening, and self-assembly of brush copolymer poly(ethylene oxide)-graft-poly(N,N-dimethylaminoethyl methacrylate) in aqueous solutions

Double hydrophilic brush copolymer poly(ethylene oxide)-graft-poly(N,N-dimethylaminoethyl methacrylate) (PEO-g-PDMAEMA) was successfully prepared via atom transfer radical polymerization (ATRP). We investigated the pH/thermoresponsive behaviors of PEO-g-PDMAEMA brush-shaped copolymer concentrated aqueous solutions by rheology. The observed LCST strongly decreased with increasing pH of the solutions, which was lower than that of linear block copolymer for different pH, indicating rapid thermoresponsiveness of the brush PDMAEMA chains. An unexpected shear thickening behavior was observed and could be tuned by the pH, resulting from the mobile nature and tractive force of the densely grafted hydrophobic chains of PDMAEMA at high pH. Self-assembly of the brush copolymer in a different pH and ionic strength environment was studied by transmission electron microscopy. A wormlike cylinder structure was formed at low pH. Fractals were observed for the brush copolymer aqueous solution in the presence of NaCl. The results showed that by adjusting the pH and NaCl concentration of the dispersions fractal aggregates with different topology were obtained. The observations reported here can supply a better understanding of the molecular self-assembling nature and be used to develop responsive materials with better performance.     

A starlike amphiphilic graft copolymer with hydrophilic poly(acrylic acid) backbones and hydrophobic polystyrene side chains

A well‐defined starlike amphiphilic graft copolymer bearing hydrophilic poly(acrylic acid) backbones and hydrophobic polystyrene side chains was synthesized by successive atom transfer radical polymerization followed by the hydrolysis of poly‐(methoxymethyl acrylate) backbone. A grafting‐from strategy was employed for the synthesis of a graft copolymer with narrow molecular weight distribution. Hydrophobic polystyrene side chains were connected to the backbones through stable C? C bonds. The poly(methoxymethyl acrylate) backbones can be easily hydrolyzed with HCl without affecting the hydrophobic polystyrene side chains. This kind of amphiphilic graft copolymer can form stable sphere micelles in water. The sizes of the micelles were dependent on the ionic strength and pH value. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3687–3697, 2007     

Novel amphiphilic graft copolymers bearing hydrophilic poly(acrylic acid) backbones and hydrophobic poly(butyl methacrylate) side chains

A novel amphiphilic graft copolymer consisting of hydrophilic poly(acrylic acid) backbones and hydrophobic poly(butyl methacrylate) side chains was synthesized by successive atom transfer radical polymerization followed by hydrolysis of poly‐(methoxymethyl acrylate) backbone. A grafting‐from strategy was employed for the synthesis of graft copolymers with narrow molecular weight distributions (polydispersity index < 1.40). Hydrophobic side chains were connected to the backbone through stable C? C bonds instead of ester connections. Poly(methoxymethyl acrylate) backbone was easily hydrolyzed to poly(acrylic acid) backbone with HCl without affecting the hydrophobic side chains. The amphiphilic graft copolymer could form stable micelles in water. The critical micelle concentration in water was determined by a fluorescence probe technique. The morphology of the micelles was preliminarily explored with transmission electron microscopy and was found to be spheres. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6857–6868, 2006     

Synthesis and characterization of graft copolymers based on poly(p-phenylene terephthalamide) backbone and well-defined polystyrene side chains

<正>A novel dualfunctional monomer,2-(2',2',6',6'-tetramethyl-piperidinyl-1'-oxy)methylbenzene-1,4-dioyl chloride hydrochloride,with two acid chloride groups for step-growth polymerization and a nitroxide group for the mediation of living radical polymerization was synthesized.It was first copolymerized with terephthaloyl chloride and p-phenylenediamine at a feed molar ratio of 1:3:4 in N-methyl-2-pyrrolidone containing 10 wt%calcium chloride at -10℃to yield a poly(p-phenylene terephthalamide) based macroinitiator,which initiated radical polymerization of styrene at 125℃to obtain a series of poly(p-phenylene terephthalamide)-g-polystyrenes.A combinatory analysis of proton nuclear magnetic resonance spectroscopy,Fourier transform infrared spectroscopy,elementary analysis,thermogravimetry and gel permeation chromatography indicated that the macroinitiator induced the radical polymerization of styrene to proceed in a well-controlled way.The molecular weight of side-chains increased with an increase of monomer conversion,and the molecular weight distribution index remained lower than 1.5.The graft copolymers showed a remarkably improved solubility in N-methyl -2-pyrrolidone and much depressed crystallinity in bulk.     

Kinetics of the photo-graft copolymerization of methoxypolyethyleneglycol methacrylate and N,N-dimethylaminoethyl methacrylate to dithiocarbamated poly(vinyl chloride)

Photo-graft copolymerization of methoxypolyethyleneglycol methacrylate (SM) and N,N-dimethylaminoethyl methacrylate (DAEM) to dithiocarbamated poly(vinyl chloride) (DTC-PVC) in cyclohexanone was carried out and the change of concentration of SM and DAEM with time were followed by thin-layer chromatography. Also, the change of concentration of DTC-groups during the photolysis of DTC-PVC was measured spectrophotometrically to determine the quantum yield of the photolysis.Simulation of the photo-graft copolymerization was carried out by substituting the quantum yield of the photolysis and other kinetic parameters such as monomer reactivity ratios, polymerization rate constants and φ factors, which were obtained separately, into equations for the photo-copolymerization. Agreement between experiment and calculation was very good.Moreover, experimental results concerning the degree of graft-polymerization and molecular weight change during the photo-copolymerization are discussed.     

Synthesis of double hydrophilic graft copolymer containing poly(ethylene glycol) and poly(methacrylic acid) side chains via successive ATRP

A well‐defined double hydrophilic graft copolymer, with polyacrylate as backbone, hydrophilic poly(ethylene glycol) and poly(methacrylic acid) as side chains, was synthesized via successive atom transfer radical polymerization followed by the selective hydrolysis of poly(methoxymethyl methacrylate) side chains. The grafting‐through strategy was first used to prepare poly[poly(ethylene glycol) methyl ether acrylate] comb copolymer. The obtained comb copolymer was transformed into macroinitiator by reacting with lithium diisopropylamine and 2‐bromopropionyl chloride. Afterwards, grafting‐from route was employed for the synthesis of poly[poly(ethylene glycol) methyl ether acrylate]‐g‐poly(methoxymethyl methacrylate) amphiphilic graft copolymer. The molecular weight distribution of this amphiphilic graft copolymer was narrow. Poly(methoxymethyl methacrylate) side chains were connected to polyacrylate backbone through stable C? C bonds instead of ester connections. The final product, poly[poly(ethylene glycol) methyl ether acrylate]‐g‐poly(methacrylate acid), was obtained by selective hydrolysis of poly(methoxymethyl methacrylate) side chains under mild conditions without affecting the polyacrylate backbone. This double hydrophilic graft copolymer was found be stimuli‐responsive to pH and ionic strength. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4056–4069, 2008     

Novel cationic pH-responsive poly(N,N-dimethylaminoethyl methacrylate) microcapsules prepared by a microfluidic technique

Novel monodisperse cationic pH-responsive microcapsules are successfully prepared using oil-in-water-in-oil double emulsions as templates by a microfluidic technique in this study. With the use of a double photo-initiation system and the adjustment of pH value of the monomer solution, cross-linked poly(N,N-dimethylaminoethyl methacrylate) (PDM) microcapsules with good sphericity and monodispersity can be effectively fabricated. The obtained microcapsule membranes swell at low pH due to the protonation of N(CH(3))(2) groups in the cross-linked PDM networks. The effects of various preparation parameters, such as pH of the aqueous monomer fluid, concentration of cross-linker, concentration of monomer N,N-dimethylaminoethyl methacrylate (DM) and addition of copolymeric monomer acrylamide (AAm), on the pH-responsive swelling characteristics of PDM microcapsules are systematically studied. The results show that, when the PDM microcapsules are prepared at high pH and with low cross-linking density and low DM monomer concentration, they exhibit high pH-responsive swelling ratios. The addition of AAm in the preparation decreases the swelling ratios of PDM microcapsules. The external temperature has hardly any influence on the swelling ratios of PDM microcapsules when the external pH is less than 7.4. The prepared PDM microcapsules with both biocompatibility and cationic pH-responsive properties are of great potential as drug delivery carriers for tumor therapy. Moreover, the fabrication methodology and results in this study provide valuable guidance for preparation of core-shell microcapsules via free radical polymerization based on synergistic effects of interfacial initiation and initiation in a confined space.     

Synthesis and investigation of the solution behavior of graft block copolymers of polyimide and poly(methyl methacrylate)

Graft copolymers with a polyimide backbone and poly(methyl methacrylate) side chains are investigated in dilute chloroform and ethyl acetate solutions via the methods of molecular hydrodynamics and optics. Copolymer samples are prepared through the “grafting from” method via atom-transfer radical polymerization with a multicenter polyimide macroinitiator. In solutions of copolymers with low degrees of functionalization Z (40%), supermolecular structures are formed as a result of interactions between the polyimide backbones. In samples with Z → 100%, the backbone is well screened by side chains; therefore, molecular solutions are formed in both solvents. The hydrodynamic and conformational behavior of samples with high functionalization degrees changes after the transition from ethyl acetate to chloroform owing to the different thermodynamic qualities of the solvents with respect to the copolymer components. In both solvents, the backbone tends to avoid contact with a poor solvent. This effect is more pronounced in the case of ethyl acetate. Macromolecules of the studied graft copolymers are characterized by high equilibrium rigidities (>40 nm) that are 10 times higher than the corresponding characteristics of aromatic polyimides.     

Surface properties and liquid crystal alignment behavior of poly(2-hydroxyethyl methacrylate) derivatives with alkyl ester side chains

Poly(2-hydroxyethyl methacrylate) derivatives with amphiphilic side chains composed of polar ester and non-polar alkyl groups (PHEMA#C, #=9, 11, 13, 15, and 17), where # is the number of carbon atoms in the alkyl side groups, were synthesized. In this paper, the influence of ester and alkyl groups on the molecular structure and wettability of the polymers were studied through varying # in the alkyl side groups. PHEMA#Cs with relatively longer alkyl side groups (#≥15) show bilayer lamellar structures with well aligned side chains giving rise to the very low surface energies, calculated from advancing contact angles, in the range of 22.7-22.8 mN/m. In contrast, PHEMA#Cs with shorter alkyl side groups with #≤13 have disordered structures on the polymer surfaces and stick-slip behavior was observed when water was used as the test liquid for the advancing contact angle measurements. Furthermore, the alignment behavior of nematic liquid crystal, 5CB on the PHEMA#C films could be correlated with the molecular structure and wettability of the polymers.     

Temperature-induced phase transition of poly(N,N-dimethylaminoethyl methacrylate-co-acrylamide)

Copolymers of N,N-dimethylaminoethyl methacrylate (DMAEMA) and acrylamide (AAm) were prepared to demonstrate a temperature-induced phase transition. Poly DMAEMA has a lower critical solution temperature (LCST) around 50°C in water. With copolymerization of DMAEMA with AAm, the LCST shifts to the lower temperature was observed, probably due to the formation of hydrogen bonds between amide and N,N-dimethylamino groups. FT-IR studies clearly show the formation of hydrogen bonds which protect N,N-dimethylamino groups from exposure to water and result in a hydrophobic contribution to the LCST. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys, 35: 595–598, 1997     

Temperature-induced chiral nematic phase changes of suspensions of poly(N,N-dimethylaminoethyl methacrylate)-grafted cellulose nanocrystals

Temperature-induced copolymers of poly(N,N-dimethylaminoethyl methacrylate)-grafted cellulose nanocrystals (PDMAEMA-grafted CNC) were synthesized by surface-initiated atom transfer radical polymerization (ATRP). The graft copolymers were characterized by thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FT-IR), and gel permeation chromatography (GPC). The size of the original CNC was 10–40 nm in width and 100–400 nm in length, as characterized by atomic force microscopy (AFM). The liquid-crystalline properties of the graft copolymers were investigated by using polarizing optical microscopy (POM). The graft copolymers exhibited fingerprint texture in lyotropic state. The temperature-induced fingerprint texture changes of PDMAEMA-grafted CNC aqueous suspensions were investigated at various temperatures. With increasing temperature, the spacing of the fingerprint lines decreases. Temperature-induced changes of PDMAEMA polymer chains result in changes of fingerprint texture.     

Characterization and degradation of the poly(methylphenylsiloxane)–poly(methyl methacrylate) graft copolymer

Poly(methylphenylsiloxane)–poly(methyl methacrylate) graft copolymers (PSXE-g-PMMA) were prepared by condensation reaction of poly(methylphenylsiloxane)-containing epoxy resin (PSXE) with carboxyl-terminated poly(methyl methacrylate) (PMMA), and they were characterized by gel permeation chromatography (GPC), infrared (IR), and ²⁹Si and ¹³C nuclear magnetic resonance (NMR). The microstructure of the PSXE-g-PMMA graft copolymer was investigated by proton spin–spin relaxation T₂ measurements. The thermal stability and apparent activation energy for thermal degradation of these copolymers were studied by thermogravimetry and compared with unmodified PMMA. The incorporation of poly(methylphenylsiloxane) segments in graft copolymers improved thermal stability of PMMA and enhanced the activation energy for thermal degradation of PMMA. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2521–2530, 1998     

Behavior of thermosensitive graft copolymer with aromatic polyester backbone and poly-2-ethyl-2-oxazoline side chains in aqueous solutions

Thermoresponsive graft copolymers with alkylene-aromatic polyester main chain and poly-2-ethyl-2-oxazoline side chains were synthesized. Two copolymer samples which differed in grafting density (0.5 and 0.7) were studied using dynamic and static light scattering and turbidimetry in aqueous solutions at concentration 0.0053?g?cm^?3. Hydrodynamic radii of scattering objects and their contribution to light scattering were obtained as a function of temperature in a wide temperature interval. Temperatures of phase separation were found out. Effect of grafting density on the copolymer behavior in aqueous solutions upon heating was determined. In particular, the phase separation temperature reduces with the decreasing grafting density.     

Synthesis of N,N-dimethylaminoethyl methacrylate copolymers with N-vinyl caprolactam and their complexing and flocculating behavior

Thermosensitive copolymers of N-vinyl carprolactam with N,N-dimethylaminoethyl methacrylate have been synthesized via free-radical polymerization, and reactivity ratios in dioxane have been estimated as 2.44 and 0.07, respectively. It has been shown that temperatures of phase separation for 1% aqueous solutions of homopolymers are close and remain virtually unchanged with the copolymer composition. The efficiency of flocculating behavior of copolymers with respect to a polystyrene latex has been estimated from the initial rate of flocculation as a function of the polyelectrolyte concentration in an acidic medium.     

Effects of concentration and pH on the thermosensitive behavior of a graft copolymer with polyimide backbone and poly(<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-dimethylamino-2-ethyl methacrylate) side chains

Aqueous solutions of the graft copolymer with a polyimide backbone and poly(N,N-dimethylamino-2-ethyl methacrylate) side chains with a molecular mass of M = 4.7 × 10⁵ and a grafting density of side chains of 0.44 are investigated by light scattering and turbidimetry. Solutions are studied in a wide concentration range of 0.0008–0.0250 g/cm³ at рН values varying from 2 to 12 for each concentration. The temperature dependences of optical transmission, scattered light intensity, and hydrodynamic radii of scattering objects are obtained. It is shown that the copolymer is thermosensitive only at pH > 8.0. A decrease in acidity of the medium at a fixed concentration of the copolymer is accompanied by a decline in temperatures corresponding to the onset and end of phase separation Т ₁ and Т ₂, leading to the narrowing of this interval. At constant рН values, temperatures Т ₁ and Т ₂ rise with solution dilution, while the phase transition interval becomes wider.