Hydrophilic Comonomers Research Articles

PH-responsive microgels containing hydrophilic crosslinking co-monomers: shell-exploding microgels through design

pH-responsive microgels are crosslinked polymer colloids that swell when the pH approaches the pK a of the particles. They have potential application for injectable gels for tissue repair and drug delivery systems. This study focuses on the pH-triggered gelation behaviour of a series of poly (EA/MAA/X) microgels. EA and MAA are ethylacrylate and methacrylic acid. Here, we investigate the effect of crosslinking monomer type (X) on microgel properties. The crosslinking monomers used were poly (ethyleneglycol) dimethacrylate (PEGD), ethyleneglycol dimethacrylate (EGD) and butanediol diacrylate (BDD). The microgel containing PEGD (m-PEGD) is a new system. The microgel containing BDD (m-BDD) was used as a control system. The concentrated microgel dispersions formed physical gels when the pH was increased to 5.3–6.7, and the polymer volume fractions (ϕ p ) were above about 0.05. Evidence from photon correlation spectroscopy (PCS) and dynamic rheology was presented for abrupt pH-triggered increases, and then decreases of the hydrodynamic diameters for m-PEGD and the microgel prepared using EGD (m-EGD). This appears to be tuneable through crosslinker structure. An unexpected gelation behaviour, which may involve a new gel state for microgels, was found for m-PEGD dispersions. Uniquely, those dispersions formed gels at pH values less than the microgel's pK a . This behaviour was linked to an outer-shell electrostatic repulsive interaction. The data point to a phenomenon, whereby the m-PEGD shells appear to explode at pH values above 7.0. The control microgel prepared, using BDD (m-BDD), did not show any evidence of shell fragmentation at any pH. That microgel has potential as a model pH-responsive microgel system in that the properties measured by PCS and rheology agreed well. To probe that system in more detail, the rheological data for m-BDD was analysed using scaling theory. The variation of the storage modulus (G') with ϕ p gave a scaling exponent of 2.0.

PH-responsive polymer–antigen vaccine bioconjugates

Protein-based vaccines play an important role in controlling infectious disease but their full clinical impact has been limited by their inability to generate a coordinated cellular CD4+ and CD8+ immune response. Vaccines that better deliver antigens to the cytosolic MHC1 display system could in principle provide a better coordinated response. Here, controlled radical polymerization was employed to prepare a diblock copolymer containing an endosomal releasing segment based on poly(propylacrylic acid) (poly(PAA)) and a hydrophilic segment containing thiol-reactive disulfide moieties for antigen conjugation. Propylacrylic acid (PAA) was polymerized in the presence of a trithiocarbonate based RAFT chain transfer agent (CTA). The resultant poly(PAA) was then employed as a macroCTA in the copolymerization of pyridyl disulfide methacrylamide (PDSMA) (thiol-reactive monomer) and N,N-dimethylacrylamide (DMA) as a hydrophilic comonomer. Copolymer compositions and molecular weights were determined via1H NMR spectroscopy and size exclusion chromatography. Native polyacrylamide gel electrophoresis (PAGE) showed a complete disappearance of the bands corresponding to free thiolated ovalbumin after conjugation to the polymer at pyridyl disulfide to thiol ratios as low as 2.5. The ability of the poly[(PAA)-b-(DMA)co(PDSMA)]–ovalbumin conjugates to activate CTLs was evaluated in vivo, tumor protection using the EG7 tumor protection model. Tumors were visible in the PBS and free ovalbumin immunized mice by day 7 but were not visible in the polyPAA–ovalbumin conjugate immunized mice until day 18. The mice immunized with the polyPAA–ovalbumin conjugate had a survival rate at day 21 of 100% versus 20% for PBS and 40% for ovalbumin immunized mice.

Effects of temperature on diffusion from PNIPA-based gels in a BioMEMS device for localized chemotherapy and hyperthermia

This paper presents the results of an experimental study of the effects of temperature on the diffusion from poly(N-isopropylacrylamide) (PNIPA)-based gels with hydrophilic (acrylamide) or hydrophobic (butyl methacrylate) co-monomers. The elutions of rhodamine dye and cancer drug, paclitaxel™ are studied over a range of temperatures in which localized chemotherapy can be combined with hyperthermia (37–45°C). Dye and drug release from the gels is shown to be well described by monolithic and membrane diffusion models. The current work introduces a multi-modal device that can potentially kill cancer cells by chemotherapy and hyperthermia. A clear advantage over prior devices is the ability to combine these two therapeutic interventions in one device. The implications of the results are discussed for the development of thermosensitive drug eluting Bio-Micro-Electro-Mechanical Systems (BioMEMS) devices that can treat cancer locally via the combined effects of chemotherapy and hyperthermia.

Controlled adsorption-desorption of cationic polymers on the surface of anionic latex particles

The complexation of anionic latex particles with two series of cationic copolymers is studied. The copolymers of the first series contain cationic and electroneutral (zwitter ion) hydrophilic units. The electrostatic adsorption of these copolymers on the surface of latex particles is accompanied by the formation of multiple salt bridges between cationic copolymer units and surface anionic groups. The dependence of ultimate adsorption on the molar fraction of cationic groups in copolymer α is described by a bell-shaped curve with a maximum at α = 0.05−0.10 and a long horizontal portion at α > 0.24. In terms of the adsorption theory of polyampholytes, such a pattern of the adsorption curve results from the compromise between the attraction of polymer chains to the surface induced by their polarization in the electric field of particles and the repulsion of like charged macromolecular units. The stability of complexes with the copolymers of the first series in water-salt media increases with an increase in α. The copolymers of the second series contain cationic and hydrophobic units. In this case, an increase in α is accompanied by a decrease in the amount of the adsorbed polymer throughout the studied α range (0.24–1). The complexes are stabilized not only via electrostatic interactions but also via hydrophobic interactions. A decrease in α decreases the role of electrostatics in stabilization of the complexes; however, this effect is compensated for by an increase in the number of hydrophobic contacts. This allows the stability of complexes to be preserved in concentrated water-salt solutions. The results of this study indicate that the stability of interfacial layers with the participation of cationic copolymers can be changed in a wide range by varying the ratio of ionic and electroneutral (hydrophilic or hydrophobic) comonomers in macromolecules.

The role of cationic monomers in emulsion polymerization

[2-(methacryloyloxy)ethyl] trimethylammonium chloride (MATMAC), and vinylbenzyl trimethyl ammonium chloride (VBTMAC) were chosen to be used as ionic comonomers in the emulsion polymerization of styrene. The cationic nature of the two comonomers is the same (quaternary ammonium salts), however the styrene derivate (VBTMAC) is more hydrophobic than the methacrylic one (MATMAC). With the more hydrophobic cationic comonomer (VBTMAC) higher conversions were obtained due to the in situ creation of an amphiphilic copolymer with styrene and faster rates of polymerization were observed by increasing the cationic comonomer concentration. The same behavior was observed with the more hydrophilic cationic comonomer (MATMAC) at concentrations up to 0.012 M. At higher concentrations the ionic strength controls the colloidal stability of the system and coagulation occurs.

Thermoresponsive polyacrylates obtained via a cascade of enzymatic transacylation and FRP or NMP

Following a cascade reaction comprising enzymatic monomer synthesis and radical polymerization, different functional poly(acrylate)s were obtained. Transacylation of methyl acrylate (MA) with diethylene glycol monoethyl ether, 1,2-propanediol or 1,2,6-hexanetriol in the presence of Novozyme 435 led to functional acrylate monomers. In a subsequent step, after filtration of the enzyme, removal of MA by distillation and eventual addition of a hydrophilic co-monomer, (2-hydroxyethyl acrylate, HEA), the mixture was copolymerized via free radical and nitroxide mediated polymerization resulting in poly(acrylate)s with predefined functionalities. Furthermore the thermoresponsive properties of the resulting copolymers are discussed with respect to the polymer composition and the molecular weight distribution.

Self‐controlled synthesis of hyperbranched poly(ether‐ketone)s from A2 + B3 approach in poly(phosphoric acid)

AbstractSelf‐controlled synthesis of hyperbranched poly(ether‐ketone)s (HPEKs) were prepared from “A2 + B3” approach by using different monomer solubility in reaction medium. 1,3,5‐Triphenoxybenzene as a hydrophobic B3 monomer was reacted with commercially available terephthalic acid or 4,4′‐oxybis(benzoic acid) as a hydrophilic A2 monomer in a hydrophilic reaction medium, polyphosphoric acid (PPA)/phosphorous pentoxide (P2O5). The resultant HPEKs were soluble in various common organic solvents and had the weight‐average molecular weight in the range of 3900–13,400 g/mol. The results implied that HPEKs were branched structures instead of crosslinked polymers. The molecular sizes and shapes of HPEKs were further assured by morphological investigation with scanning electron microscopy (SEM) and atomic force microscopy (AFM). Hence, the applied polymerization condition was indeed strong enough to efficiently facilitate polycondensation via “direct” Friedel‐Crafts reaction without gelation. It could be concluded that the polymer forming reaction was kinetically controlled by automatic and slow feeding of the hydrophobic B3 monomer into the hydrophilic reaction mixture containing hydrophilic comonomer. As a result, hyperbranched structures were formed instead of crosslinked polymers even at full conversion (equifunctional monomer feed ratio). © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3326–3336, 2009

Facile synthesis of triple‐stimuli (photo/pH/thermo) responsive copolymers of 2‐diazo‐1,2‐naphthoquinone‐mediated poly(N‐isopropylacrylamide‐co‐N‐hydroxymethylacrylamide)

AbstractA series of poly(N‐isopropylacrylamide‐co‐N‐hydroxymethylacrylamide) P(NIPAM‐co‐NHMA) copolymers were firstly synthesized via free radical polymerization. Then, the hydrophobic, photosensitive 2‐diazo‐1,2‐naphthoquinone (DNQ) molecules were partially and randomly grafted onto P(NIPAM‐co‐NHMA) backbone through esterification to obtain a triple‐stimuli (photo/pH/thermo) responsive copolymers of P(NIPAM‐co‐NHMA‐co‐DNQMA). UV‐vis spectra showed that the lower critical solution temperature (LCST) of P(NIPAM‐co‐NHMA) ascended with increasing hydrophilic comonomer NHMA molar fraction and can be tailored by pH variation as well. The LCST of the P(NIPAM‐co‐NHMA) went down firstly after DNQ modification and subsequently shifted to higher value after UV irradiation. Meanwhile, the phase transition profile of P(NIPAM‐co‐NHMA‐co‐DNQMA) could be triggered by pH and UV light as expected. Thus, a triple‐stimuli responsive copolymer whose solution properties could be, respectively, modulated by temperature, light, and pH, has been achieved. These stimuli‐responsive properties should be very important for controlled release delivery system. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2763–2773, 2009

Equilibrium Swelling Studies of Highly Swollen Acrylamide/Thiosinamine Hydrogels

Highly swollen water absorbent copolymers on acrylamide (AAm) and thiosinamine (ThA) have been studied as a function of copolymer composition. AAm/ThA hydrogels were prepared by free radical solution polymerization in aqueous solution of AAm with ThA as hydrophilic comonomer and two multifunctional crosslinkers such as 1,4 butanediol dimethacrylate (BDMA) and trimethylolpropane triacrylate (TMPTA). Swelling experiments were performed in water at 25°C, gravimetrically. The influence of ThA content in hydrogels was examined. Swelling of AAm/ThA hydrogels was increased up to 2156% (for containing 20 mg ThA and crosslinked by TMPTA) and 3139% (for containing 20 mg ThA and crosslinked by BDMA), while AAm hydrogels swelled up to 1155% (crosslinked by TMPTA) − 1417% (crosslinked by BDMA). The values of equilibrium water content of the hydrogels are 0.9203-0.9691. Diffusion behavior was investigated. Water diffusion into hydrogels was found to be non-Fickian in character.

Adhesive Bonding to Dentin Improved by Polymerizable Cyclodextrin Derivatives.

The objective of this work was to determine bonding characteristics of a hydrophilic monomer formulation containing polymerizable cyclodextrin derivatives. The hypothesis was that a formulation containing hydrophilic cross-linking diluent comonomers and cyclodextrins with functional groups attached by hydrolytically stable ether linkages could form strong adhesive bonds to dentin. The previously synthesized polymerizable cyclodextrin derivatives were formulated with sorbitol dimethacrylate, methacrylic acid and phenylbis(2,4,6-trimethylbenzoyl) phosphine oxide photoinitiator. The same formulation without the polymerizable cyclodextrin derivatives isolated the effects of the polymerizable cyclodextrin derivatives. A commercial self-etching bonding system was tested as a comparative control. Ground mid-coronal dentin was etched with 37 % phosphoric acid (H3PO4) for 15 s and rinsed with distilled water for 10 s. Formulations were applied to the moist dentin and light-cured 10 s. A packable composite was then applied through irises and light-cured 60 s. Teeth were stored in water for 24 h before bonds were tested in a shearing orientation. One-way ANOVA was performed on the data. The average values of shear bond strengths were defined as loads at fracture divided by the 4 mm diameter iris areas. The average value of shear bond strength for the formulation containing the polymerizable cyclodextrin derivatives was higher (p < 0.05), where p is a fraction of the probability distribution) than that of the same monomeric formulation except that the polymerizable cyclodextrin derivatives were not included. This was supporting evidence that the polymerizable cyclodextrin derivatives contributed to improved bonding. The average value of shear bond strength for the formulation containing the polymerizable cyclodextrin derivatives was also higher (p < 0.05) than that of the commercial self-etching bonding system. These preliminary results are in accordance with the hypothesis that formulations containing polymerizable cyclodextrin derivatives can form strong adhesive bonds to hydrated dentin surfaces. Further improvements in bonding to hydrated biological tissues by use of advanced formulations are anticipated.

Magnetic mesoporous silica microspheres with thermo-sensitive polymer shell for controlled drug release

A controlled drug release system was designed based on the combination of three advantages into one entity, which was composed of Fe3O4 magnetic nanoparticle as the core, mesoporous silica as the sandwiched layer, and thermo-sensitive P(NIPAM-co-NHMA) copolymer as the outer shell. The hydrophilic comonomer content affected the volume phase-transition temperature (VPTT) of this composite microsphere and the behavior of the temperature-triggered drug release. Zn(II) phthalocyanine tetrasulfonic acid (ZnPcS4), a well-known photodynamic therapy (PDT) drug, was used as a model drug to assess the release system. The results demonstrated that the drug release behavior was dependent on the temperature and had a close correlation with the VPTT. Above the VPTT, the drug release rate was much faster than that below the VPTT, which showed a great potential application in tumor therapy.

The Effects of Interfacial Tensions of Amphiphilic Copolymers on Honeycomb-Patterned Films

A honeycomb-patterned film is formed by casting a polymer solution of polystyrene and amphiphilic copolymer under humid condition. Amphiphilic copolymers stabilize condensed water droplets as temporal templates. Therefore, physical properties of the amphiphilic copolymer are important factors for stability of condensed water droplets and the structure of the honeycomb-patterned film. In order to verify the effect of the interfacial tension between water and chloroform solution of the amphiphilic copolymer, which is one of the important physical properties, amphiphilic copolymers were synthesized from hydrophobic monomer and hydrophilic monomer at various copolymerization ratios. The interfacial tension decreased with increasing the copolymerization ratio of the hydrophilic comonomer. Uniformity of micropores of the honeycomb-patterned film increased with decreasing the value of the interfacial tension. Moreover, polymer frame of honeycomb-patterned film became thinner with decreasing the value of the interfacial tension. These results indicate that the structure of honeycomb-patterned film can be controlled by the interfacial tension between water and polymer solution.

Preparation of nanoencapsulated phase change material as latent functionally thermal fluid

Nanoencapsulated phase change material with polystyrene as the shell and n-octadecane as the core was synthesized using the ultrasonic technique and miniemulsion in situ polymerization. The influences of polymerization factors, including initiator, chain transfer agent (CTA), surfactant, n-octadecane/styrene ratio and hydrophilic co-monomer, on the morphology and thermophysical properties of nanocapsules were systematically investigated. The optimized polymerization conditions were 0.5 wt% of initiator (2,2-azobisisobutyronitrile), 0.4 wt% of CTA (n-dodecyl mercaptan), 2% of composite surfactants which were composed of sodium dodecyl sulfate and poly-(ethylene glycol) monooctylphenyl ether by 1 : 1 in weight ratio, 1 wt% of hydrophilic co-monomer butyl acrylate or 3 wt% of methyl methacrylate and 1 : 1 n-octadecane to styrene in weight ratio. Under these conditions, the z-average size of prepared nanocapsules was 124 nm and the phase change enthalpy was 124.4 kJ kg−1. The heat capacity was as high as 11.61 kJ kg−1 K−1 at the latex concentration of 20.6 wt%. Thermal stability and viscosity testing show that this fluid had excellent resistance to thermal shock (after 100 cycles, no liquid Oct was observed during heating) and low viscosity (only 3.61 mPa s at the latex concentration of 20.6 wt%), which seems to be promising as a latent functionally thermal fluid.

Facile synthesis of functional silica/polymer composite materials and hydrophilic hollow polymer microspheres

AbstractMonodisperse functional silica/polymer core‐shell composite materials with silica as core and hydrophilic polymer with various functional groups, such as amide, carboxylic acid, hydroxyl, and pyridyl group, as shell were facilely prepared by a two‐stage reaction, in which the silica core with diameter of 179 nm was synthesized in the first‐stage reaction according to the Stöber method. The functional polymer shell was then encapsulated onto the silica core by distillation–precipitation copolymerization of N,N′‐methylenebisacrylamide (MBAAm) as crosslinker and hydrophilic comonomers with different functional groups, including N‐isopropylacrylamide, methacrylic acid, 2‐hydroxyethyl methacrylate, and 4‐vinylpyridine, in neat acetonitrile with 2,2′‐azobisisobutyronitrile as initiator. The encapsulation of the functional polymer shell onto the silica core particles was driven by the hydrogen‐bonding interaction between the hydroxyl group on the surface of silica core and the amide unit of MBAAm crosslinker as well as the functional groups of the comonomers during the distillation–precipitation polymerization without modification of the silica surface in absence of any stabilizer or surfactant. The shell thickness of the composite can be controlled by MBAAm fraction in the monomer feed during the polymerization. Hydrophilic hollow polymer microspheres with various functional groups, including amide, carboxylic acid, hydroxyl, and pyridyl, were further developed after selective removal of silica core with hydrofluoric acid. The functional core‐shell silica/polymer composites and the corresponding functional hollow microspheres were characterized with transmission electron microscopy, Fourier transform infrared spectra, and dynamic light scattering. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

HYDROGELS FROM N,N'-DIMETHYLACRYLAMIDE-co-2-ACRYLAMIDO-2-METHYL-1-PROPANESULFONIC ACID WITH SALT-, TEMPERATURE- AND pH-RESPONSIVENESS PROPERTIES

The synthesis of copolymer hydrogels of N, N′-dimethylacrylamide (NNDMAAm) with 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) were prepared by solution free radical polymerization at different feed mole ratios (mole ratios of n NNDMAAm /n AMPS = 0.5/0.5; 0.33/0.66; 0.66/0.33; 0.25/0.75; 0.75/0.25). In this reaction ammonium persulfate (APS) and N,N´-methylene-bis-acrylamide (MBA) were used as initiator and cross-linking reagents respectively. These copolymers were insoluble in water and it were characterized by elemental analysis, FT-IR spectroscopy, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). Aqueous solutions of the copolymers showed lower critical solution temperature behavior (LCST). The phase transition temperatures of aqueous solutions of these copolymers increased with increasing of hydrophilic AMPS comonomer content in the copolymers. The effects of reaction parameters, including the concentration of cross-linking reagent, the monomer concentration, pH, temperature, salt solutions, and solvent polarity on the water absorption have been also studied. Under the experimental conditions, the copolymer poly(NNDMAAm-co-AMPS) with a feed mol ratio 1:2 presents the best swelling properties. The monomer reactivity ratios for poly(NNDMAAm-co-AMPS) are the following: r 1 = 0.217 and r 2 = 2.20, (r 1 x r 2 = 0.48).

Synthesis and properties of propene copolymers with ether comonomers

The direct copolymerization of propene with polar comonomers using metallocene catalysts in solution was investigated. As comonomers, two ether compounds were used in comparison to 10-undecene-1-ol as well-investigated comonomer. The ether comonomers were diethylene glycol mono-10-undecenyl ether (DEGUE) and octaethylene glycol-10-undecenyl methyl ether (OEGUME). The influence of the different comonomers on the copolymerization behavior was studied. The copolymers were characterized with respect to their comonomer contents, molar masses, and thermal properties. The incorporation rate of DEGUE and OEGUME into the propene copolymers did not exceed 1.6mol% for DEGUE and 0.31mol% for OEGUME and was thus considerably lower than in the reference propene copolymerization with 10-undecene-1-ol. An uncompleted shielding of the oxygen atoms of the ether groups by triisobutyl aluminum (TIBA) to the metallocene catalyst is assumed to be responsible for this behavior. The crystallization kinetics in the copolymers with comparable molar masses is mainly influenced by the side chain density per 1000 propene units, n1000.The incorporation of hydrophilic comonomers into polypropene was expected to alter the surface properties. The slightly lowered water contact angles found on films of copolymers with higher comonomer content indicated the enhanced hydrophilicity of the polypropene copolymer surfaces compared to polypropene (PP).

Preparation and characterization of 2‐hydroxyethyl methacrylate‐based porous copolymeric particles

Abstract2‐Hydroxyethyl methacrylate was copolymerized with three different comonomers, methyl methacrylate (MMA), styrene (St), and N‐vinyl‐2‐pyrrolidone (NVP), respectively, to prepare porous particles crosslinked using ethylene glycol dimethacrylate (EGDMA) in the presence of an organic solvent, 1‐octanol (porogen), by means of suspension copolymerization in an aqueous phase initiated by 2,2‐azobisisobutyronitrile. Nano‐pores were observed in the particles. The pore size and the swelling properties of these particles can be controlled by changing comonomers or adjusting the crosslinker or porogen concentration. A lower crosslinker or porogen concentration favors generating smaller pores, whereas a higher concentration of a hydrophilic comonomer, higher concentration of crosslinker, and higher porogen volume ratio promote the generation of larger pores. In addition, the effects of the porous characteristics on the swelling properties were explored. The swelling capacity of the porous particles is reduced with the increase in the crosslinker concentration; however, there is a critical porogen volume ratio, in which the maximal swelling capacity is reached. Higher porosity in the particles and higher amount of hydrophilic comonomer favor a higher swelling capacity of the particles. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

Effect of Hydrophilic Comonomer and Surfactant Type on the Colloidal Stability and Size Distribution of Carboxyl- and Amino-Functionalized Polystyrene Particles Prepared by Miniemulsion Polymerization

Carboxyl and amino-functionalized polystyrene latex particles were synthesized by the miniemulsion copolymerization of styrene and acrylic acid or 2-aminoethyl methacrylate hydrochloride (AEMH). The reaction was started by using an oil-soluble initiator, such as 2,2'-azobis(2-methylbutyronitrile) (V-59). The effect of the functional monomer content and type of surfactant (non-ionic versus ionic) on the particle size and particle size distribution was investigated by dynamic light scattering (DLS) and transmission electron microscopy (TEM). A bimodal particle size distribution was observed for functionalized latex particles prepared in the presence of the non-ionic surfactant (i.e., Lutensol AT-50) when 1 wt % of acrylic acid or 3 wt % of AEMH as a comonomer was employed. The copolymer particle nucleation was studied by using a highly hydrophobic fluorescent dye. From the obtained results, the formation of bimodal particle size distribution may be attributed to a budding-like effect, which takes place during the earlier stage of polymerization and is caused by the additional stabilizing energy originated from the ionic groups of a functional polymer. The reaction mechanism of particle formation in the presence of non-ionic and ionic surfactants has been proposed. The amount of the surface functional groups was determined from polyelectrolyte titration data.

Precise Control of Lower Critical Solution Temperature of Thermosensitive Poly(2-isopropyl-2-oxazoline) via Gradient Copolymerization with 2-Ethyl-2-oxazoline as a Hydrophilic Comonomer

The lower critical solution temperature (LCST) of amphiphilic poly(2-isopropyl-2-oxazoline) (PiPrOx) was precisely tuned via the copolymerization with 2-ethyl-2-oxazoline (EtOx) as a hydrophilic comonomer. The copolymerization was cationically initiated by methyl p-tosylate at the optimum condition (42 °C in acetonitrile) for living polymerization, obtaining the copolymers with a narrow molecular weight distribution (Mw/Mn ≤ 1.02). The monomer reactivity ratios of 1.78 and 0.79 respectively were derived for EtOx and iPrOx from the cumulative and instantaneous compositions of the copolymers determined from the 1H NMR and MALDI-TOF mass spectrometry. This set of the reactivity ratios are sufficiently different enough to form the gradient copolymers, in which each polymer chain has a trend of a gradually decreasing EtOx and an increasing iPrOx composition along the backbone from the α-terminal to ω-chain end. These gradient copolymers followed a rather simple rule in their thermosensitive behaviors to show a...

Biomimetic condensation copolyesters

Copolyterephthalates of bis(4-hydroxy-3-methylphenyl)-2,2-propane and N-methyldiethanolamine and their hydrochloric salts of various compositions and microstructures have been prepared by the copolycondensation of hydrophilic and hydrophobic comonomers. It has been shown that the transition from random proteinlike structures to the block structures makes it possible to preserve biomimetic properties of the copolymers at a smaller content of charged units in macromolecules. The ability of charged polymers to survive in aqueous solutions has been used for the synthesis of copolyterephthalate of N-bis(hydroxyethyl)tetradecylmethylammonium bromide and N-methyldiethanolamine demonstrating fungicidal activity.