Synthesis, characterization and evaluation of amphiphilic star copolymeric emulsifiers based on methoxy hexa(ethylene glycol) methacrylate and benzyl methacrylate

Amphiphilic star copolymers were synthesized by sequential monomer and cross-linker additions using group transfer polymerization (GTP). Benzyl methacrylate (BzMA) and methoxy hexa(ethylene glycol) methacrylate (HEGMA) served as the hydrophobic and hydrophilic monomers, respectively, whereas the also hydrophobic ethylene glycol dimethacrylate (EGDMA) was used as the cross-linker. In total, twelve star copolymers were prepared, covering three different overall hydrophobic compositions, 39, 53 and 70% w/w, and four different architectures, AB star-block, BA star-block, heteroarm star and random star. The theoretical molecular weight of each arm was kept constant at 5000 g mol⁻¹. The molecular weights and molecular weight distributions of the linear precursors and of all the star copolymers were characterized by gel permeation chromatography (GPC) in tetrahydrofuran (THF), while their compositions were confirmed by proton nuclear magnetic resonance (¹H NMR) spectroscopy. Moreover, all the star copolymers were characterized by static light scattering (SLS) in THF to determine the absolute weight-average molecular weight, M_w, and the weight-average number of arms. After polymer characterization, xylene-water and diazinon (pesticide)-water emulsions were prepared using these star copolymers as stabilizers at 1% w/w copolymer concentration and at different overall organic phase/water ratios. The most important factor in determining the emulsion type was the star copolymer composition in hydrophobic units. The four most hydrophilic star copolymers (39% w/w hydrophobic composition) always formed o/w emulsions, while the four most hydrophobic star copolymers (70% w/w hydrophobic composition) always formed w/o emulsions. The type of the emulsion in the case of the star copolymers with the more balanced composition, 53% w/w hydrophobic units, also depended on the emulsion content in the organic solvent, similar to particulate-stabilized emulsions. Considering that the best o/w emulsifier is that star copolymer which can emulsify the largest quantity of organic phase in water resulting in low viscosity, o/w emulsions without excess oil or water phase, it appeared that the most hydrophilic random copolymer star is the optimal emulsifier. Moreover, this star copolymer presented the smallest droplet size in its emulsions. It is also noteworthy that the resulting emulsions almost never had high viscosity, a feature attributable to the compact nature of star polymers.     

Synthesis and evaluation of a star amphiphilic block copolymer from poly(ε‐caprolactone) and poly(ethylene oxide) as load and release carriers for guest molecules

The use of polymeric materials as the carrier in the controlled release of guest molecules has become an important research area in the polymeric materials science, because of their advantages of the safety, efficacy and patient convenience. One of them, star amphiphilic polymer can self‐assemble into supermolecular structure (polymer micelles) by the balance of hydrophilic and hydrophobic interaction. In this study, star amphiphilic copolymer consisting of hydrophobic and biodegradable poly(ε‐caprolactone) (PCL) and hydrophilic poly(ethylene oxide) (PEO) blocks were synthesized by two‐step ring‐opening polymerization. The resultant polymer was characterizated by FTIR, ¹H‐NMR, and DSC to determine its chemical structure. The morpholoy of the polymer micelles was analyzed by TEM. Using star‐PCL‐b‐PEO as carriers and congo red as model guest molecules, the encapsulation and release properties were investigated by UV–visable analysis. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Conformation of polyacrylamide in aqueous solution with interactive additives and cosolvents

The viscosity of polyacrylamide (PAM) dilute aqueous solutions with NaCl, glucose, and SDS as additives was measured by Ubbelohde viscometry. There was linear relationship between reduced viscosity vs. PAM concentration in aqueous solutions. The Huggins constant k and intrinsic viscosity [η] were used to study the conformation of the polymer chains and the degree of polymer–solvent interaction. In addition, the viscosity of diluted PAM solutions in water with acetone, ethanol, DMF, and ethylene glycol as cosolvent was measured. It was found that the polymer chain conformation contracted as the acetone, ethanol, and DMF cosolvent composition ratio increased, but there was no distinguishing difference between water–ethylene glycol compositions. The solution properties of PAM were used to estimate the swelling properties of PAM gel in the same external conditions, as gel is formed by crosslinking of linear polymer. In good solvent the polymer chain should be expanded, and gel is expected to have large swelling ratio. In water cosolvent systems, when the linear polymer chain underwent coil–globule transition, PAM gel should have volume phase transition under corresponding external conditions. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3122–3129, 2003     

Effect of molecular architecture on the self-diffusion of polymers in aqueous systems: A comparison of linear, star, and dendritic poly(ethylene glycol)s

Star polymers with a hydrophobic cholane core and four poly(ethylene glycol) (PEG) arms, CA(EG_n)₄, have been synthesized by anionic polymerization. Pulsed-gradient spin-echo NMR spectroscopy was used to study the diffusion behavior of the star polymers, ranging from 1000 to 10,000 g/mol, in aqueous solutions and gels of poly(vinyl alcohol) (PVA) at 23 °C. The star polymers have a lower self-diffusion coefficient than linear PEGs at equivalent hydrodynamic radius. In water alone, the star polymers and their linear homologues have a similar diffusion behavior in the dilute regime, as demonstrated by the similar concentration dependence of the self-diffusion coefficients. In the semidilute regime, the star polymers tend to aggregate due to their amphiphilic properties, resulting in lower self-diffusion coefficients than those of linear PEGs. ¹H NMR T₁ measurements at 10-70 °C revealed that the PEG arms of the star polymers are more mobile than the core, suggesting the star polymers in solution have a conformation similar to that of poly(propylene imine) dendrimers.     

Gel electrolytes with ionic liquid plasticiser for electrochromic devices

The comparative performance of conducting polymer electrochromic devices (ECDs) utilising gel polymer electrolytes (GPEs) plasticised with ethylene carbonate/propylene carbonate or (N-butyl-3-methylpyridinium trifluoromethanesulphonylimide (P₁₄TFSI) has been made. Lithium perchlorate and lithium trifluoromethanesulphonylimide salts were used in the GPEs to provide enhanced ionic conductivity and inhibit phase separation of the polyethyleneoxide (PEO) and plasticiser. ECDs were assembled from cathodically colouring, polyethylenedioxythiophene (PEDOT), and anodically colouring, polypyrrole (PPy), conducting polymer electrochromes deposited by vapour deposition. The photopic contrast switching over the visible light spectrum, switching speeds and device stability of the ECDs were obtained. These studies demonstrate that the ionic liquid (IL) plasticised GPEs are a suitable replacement for pure IL based devices and volatile organic solvent plasticisers based upon ethylene carbonate/propylene carbonate mixtures.     

Star poly(2‐ethyl‐2‐oxazoline)s—synthesis and thermosensitivity

A series of star‐shaped poly(2‐ethyl‐2‐oxazoline)s was prepared by cationic polymerization. The polymerization was initiated by dipentaerythrityl hexakis(4‐nitrobenzene sulfonate) and a tosylated hyperbranched polymer of glycidol. The polymerization proceeded in a controlled manner. The star structure of the products was determined by nuclear magnetic resonance. The molar mass distributions that were measured by gel permeation chromatography with multiangle laser light scattering were narrow, and the experimental values of the molar masses were close to those predicted. The very compact structure of the polymers obtained (compared with the linear counterparts) confirmed the star formation. The star poly(2‐ethyl‐2‐oxazoline)s show a phase transition temperature in the range 62–75 °C. Comparison of this phase transition temperature with that of the linear poly(2‐ethyl‐2‐oxazoline)s with the same molar masses indicates the influence of molar mass and topological structure of the macromolecule on temperature behavior. The prepared copolymers are spherical, which might be useful for the controlled transport and release of active compounds. Copyright © 2011 Society of Chemical Industry     

Rheological characterization of the gel point in polymer‐modified asphalts

In this work, the rheological characterization of the gel point in polymer‐modified asphalts is carried out. The viscoelastic properties of polymer‐modified asphalts, in which the polymer is styrene–ethylene butylene–styrene (SEBS) with grafted maleic anhydride (MAH), were measured as a function of MAH concentration. The crosslinking reaction that leads to gelation is characterized by power‐law frequency‐dependent loss and storage modulus (G″ and G′). The relaxation exponent n (a viscoelastic parameter related to the cluster size of the gel) and gel strength S (related to the mobility on the crosslinked chain segments) were determined. The value of the power‐law exponents depends on the composition of polymer, ranging from 0.30 to 0.56, while the value of the rigidity modulus at the gelation point (S) increases with the amount of reactive groups of the modifier polymer. Both n and S are temperature‐dependent in the blends. The blends containing gels present a coarse morphology, which is related to the rheological properties of the matrix and dispersed phase. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

聚间苯二甲酰间苯二胺平板膜的制备及其性能研究

以聚间苯二甲酰间苯二胺（PMIA）为制膜原料,氯化锂（LiCl）、聚乙二醇（PEG-400）和聚乙烯吡咯烷酮（PVP）为添加剂,通过非溶剂诱导相转化法制备了PMIA平板膜,系统考察了聚合物浓度、添加剂种类和含量对PMIA膜结构和性能的影响。结果表明,聚合物浓度和LiCl含量增加,铸膜液黏度增大,导致膜孔径减小,纯水通量降低。而PEG含量的增加,使得聚合物链呈现舒展状态,膜孔径增大,纯水通量升高,亲水性增强。随着PVP含量的增加,膜的纯水通量先升高后降低,膜的亲水性变差。当PMIA的质量分数为9%,LiCl的质量分数为2.8%,PVP的质量分数为1.2%时,膜的纯水通量高达1421.55 L·m^-2·h^-1·bar^-1,对牛血清蛋白（BSA）的截留率为80%,展现出较高的渗透性,为制备高性能膜材料提供了新的思路。     

聚间苯二甲酰间苯二胺平板膜的制备及其性能研究

以聚间苯二甲酰间苯二胺（PMIA）为制膜原料,氯化锂（LiCl）、聚乙二醇（PEG-400）和聚乙烯吡咯烷酮（PVP）为添加剂,通过非溶剂诱导相转化法制备了PMIA平板膜,系统考察了聚合物浓度、添加剂种类和含量对PMIA膜结构和性能的影响。结果表明,聚合物浓度和LiCl含量增加,铸膜液黏度增大,导致膜孔径减小,纯水通量降低。而PEG含量的增加,使得聚合物链呈现舒展状态,膜孔径增大,纯水通量升高,亲水性增强。随着PVP含量的增加,膜的纯水通量先升高后降低,膜的亲水性变差。当PMIA的质量分数为9%,LiCl的质量分数为2.8%,PVP的质量分数为1.2%时,膜的纯水通量高达1421.55 L·m^-2·h^-1·bar^-1,对牛血清蛋白（BSA）的截留率为80%,展现出较高的渗透性,为制备高性能膜材料提供了新的思路。     

New thermogelling poly(organophosphazenes) with methoxypoly(ethylene glycol) and oligopeptide as side groups

A new class of thermogelling poly(organophosphazenes) bearing a hydrophilic methoxypoly(ethylene glycol) (MPEG) and a hydrophobic tri or tetrapeptide such as GlyPheLeuEt, GlyPheIleEt, GlyLeuPheEt, and GlyPheLeuGlyEt have been synthesized and characterized by means of multinuclear (¹H, ³¹P) NMR spectroscopy, gel permeation chromatography, viscometry, and elemental analysis. The gelation of the present polymers is presumed to be attributed to the intermolecular interaction between the hydrophobic oligopeptide side groups, which can form strong physical junction zones in the polymer aqueous solution. The gelation properties of the polymer were affected by the subtle change in the nature of the hydrophobic oligopeptide, composition of the hydrophilic to hydrophobic side groups, and the concentration of the polymer solutions. Among the present thermogels, the copolymer with equimolar MPEG and GlyPheIleEt as side groups showed the excellent gel phase persisting over 35-43 °C, which indicates that it is a new promising material for drug delivery and tissue engineering.     

Amphiphilic star block copolymers: Influence of branching on lyotropic/interfacial properties

How can the degree of branching influence the lyotropic properties of amphiphilic block copolymers? In order to provide a qualitative answer to this question, we have prepared a library of poly(propylene sulfide)-bl-poly(ethylene glycol) (PPS-PEG) block copolymers, varying the hydrophobic block (PPS) length and its branching degree and thus producing diblock, triblock (that can be seen as two-armed star), tri-armed star and tetra-armed star structures. The PEG block, on the contrary, was kept constant (linear PEG2000).Although all the polymers exhibited a qualitatively similar lyotropic behaviour, an increased degree of branching of the hydrophobic block caused clear differences in the rheology of lyotropic phases, with an increasingly softer character, and in the organisation of the PEG chains, which appeared to adopt possibly more extended and dehydrated conformations.     

Perfluoroalkyl‐terminated star polymer electrolyte

A perfluoroalkyl‐terminated multiarm star polymer (perfluoroalkyl‐terminated hyperbranched polyglycerol) was synthesized and characterized on the basis of perfluorooctanoyl chloride grafting on hyperbranched polyglycerol. The conductivity of a blend of the perfluoroalkyl‐terminated star polymer and linear poly(ether urethane) was studied. The results indicated that this blend had better solvating capability in salt and higher ionic conductivity. The conductivity of the blend was 2.5 × 10^?4 S cm^?1 at 60°C when the concentration of the perfluoroalkyl‐terminated hyperbranched polyglycerol was 30 wt % and the ethylene oxide (EO)/Li ratio was 4 in the blend. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 238–242, 2005     

Interaction between a tertiary amine methacrylate based polyelectrolyte and a sodium montmorillonite dispersion and its rheological and colloidal properties

The rheological and colloidal properties of sodium montmorillonite dispersions were investigated in the presence of a special type of cationic polymer [modified poly(ethylene glycol)]. 2‐(Dimethylamino) ethyl methacrylate was polymerized with monomethoxy‐capped oligo(ethylene glycol) via aqueous atom transfer radical polymerization. The tertiary amine residues of the resulting polymer were then quaternized with methyl iodide to obtain a cationic polyelectrolyte. The rheology and ζ‐potential experiments showed that the cationic polymer adsorbed onto the sodium montmorillonite surface strongly. The rheological parameters (plastic viscosity and yield value) were obtained with a rotational low‐shear rheometer. The results indicated a gradual increase in gelation with the addition of the cationic polymer, which reached a maximum at a cationic polymer concentration of 0.4–0.8 g/L. This gel‐like dispersion showed pronounced thixotropy. A further increase in the polymer concentration resulted in a reduction in this gelation. The adsorption of the cationic polymer onto the clay surface reduced the ζ potential to small values, but no isoelectric point was observed. The basal‐spacing measurements showed that the cationic polymer strongly adsorbed onto the sodium montmorillonite instead of entering the montmorillonite layers. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 300–306, 2005     

Star polymers with random number of temperature sensitive arms and crosslinked poly(EGDMA)-core and their application to drug delivery

A simple methodology is described for the preparation of temperature sensitive star polymers with random number of arms and crosslinked core. In the first step, well defined, monodisperse poly(N-isopropylacrylamide) PNIPAAm polymers were prepared by reversible addition–fragmentation chain transfer polymerization (RAFT-polymerization) by using 4-cyanopentanoic acid dithiobenzoate as chain transfer agent (CTA). In the second step, the PNIPAAm polymers were used as macro-CTA’s for copolymerization with ethylene glycol dimethacrylate (EGDMA) by the RAFT-technique. Adjusting the macro-CTA to EGDMA ratio, nanometric star polymers with small or big core could be prepared as revealed by gel permeation chromatography (GPC), dynamic light scattering (DLS) and viscometry. The same methodology was applied for the preparation of star polymers with poly(NIPAAm)-b-poly(hexyl acrylate) arms. The so prepared temperature sensitive multiarm materials are a stable alternative to polymeric micelles as nano-carriers for drug-delivery applications.     

Degradation of azo-containing polyurethane by the action of intestinal flora: its mechanism and application as a drug delivery system

Several segmented polyurethanes comprising azo aromatic and hydrophilic groups were synthesized by reaction of m-xylylene diisocyanate with a mixture of m,m′-dihydroxyazobenzene, poly(ethylene glycol) (PEG, M_a = 2000) and 1,2-propanediol (propylene glycol, PG). Their polymer films were made by solution casting, and pellets of a hydrophilic drug (FOY-305) were coated with these polymers. Both the films and the coated pellets were incubated anaerobically in a culture of human intestinal flora. It was found that the azo groups in the polymer were reduced to hydrazo groups during incubation, which induced degradation of the films and the coatings without decreasing the molecular weight of the polymer. The rate of drug release from the pellets depended on both the azo and PEG compositions. Based on these findings, a new degradation mechanism of the polyurethane films and coatings is proposed.     

Synthesis,characterization and surface properties of star‐shaped polymeric surfactants with polyhedral oligomeric silsesquioxane core

Star‐shaped amphiphilic polymeric surfactants comprising a hydrophobic polyhedral oligomeric silsesquioxane (POSS) core and hydrophilic poly(ethylene glycol) (PEG) arms with various chain lengths are successfully synthesized using copper(I)‐catalysed azide–alkyne cycloaddition (CuAAC) click reaction. Their chemical structures and molecular characteristics are clearly confirmed using Fourier transform infrared and ¹H NMR spectroscopies and gel permeation chromatography, and no homopolymer is found after CuAAC click reaction. Aqueous solutions of these star‐shaped polymers have been investigated using atomic force and transmission electron microscopies and dynamic light scattering studies and it is found that they can self‐assemble into micelles. The sizes of the micelles can be adjusted by the length of the PEG arms, where longer chains not only lead to increased micelle sizes, but also reduce the contact angle values. Moreover, the melting points and root mean square roughness of the obtained star‐shaped polymers are slightly increased on increasing the chain length of the PEG arms. © 2017 Society of Chemical Industry     

Preparation of pH-sensitive amphiphilic block star polymers,their self-assembling characteristics and release behavior on encapsulated molecules

Poly(ethylene glycol) (PEG), a polymer with excellent biocompatibility, was widely used to form nanoparticles for drug delivery applications. In this paper, based on PEG, a series of pH-sensitive amphiphilic block star polymers of poly(ethylene glycol)-block-poly(ethoxy ethyl glycidyl ether) (PEG-b-PEEGE) with different hydrophobic length were synthesized by living anionic ring-opening polymerization method. The products were characterized using ¹H NMR and gel permeation chromatography. These copolymers could self-assemble in aqueous solution to form micellar structure with controlled morphologies. Transmission electron microscopy showed that the nanoparticles are spherical or rodlike with different hydrophilic mass fractions. The pH response of polymeric aggregates from PEG-b-PEEGE was detected by fluorescence probe technique at different pH. A pH-dependent release behavior was observed and pH-responsiveness of PEG-b-PEEGE was affected by the hydrophobic block length. These results demonstrated that star-shaped polymers (PEG-b-PEEGE) are attractive candidates as anticancer drug delivery carriers.     

Synthesis and characterization of thermosensitive poly(organophosphazene) gels with an amino functional group

Thermosensitive poly(organophosphazene) gels have been synthesized with a host of side groups, including α‐amino‐ω‐methoxy‐poly(ethylene glycol), hydrophobic amino acid esters (PheOEt, LeuOEt, and IleuOEt), depsipeptide ethyl ester (GlyGlycOEt), and lysine ethyl ester (lysOEt). The fraction of the last side group, lysOEt, which possesses two amine functional groups, was designed to be in the range of 0.1–0.3 mol per polymer unit. The poly(organophosphazenes) have been characterized via ¹H‐ and ³¹P‐NMR spectroscopies, GPC, and elemental analysis. The phase transition behavior of the poly(organophosphazenes) in aqueous solution has been determined via viscometry. Some of the poly(organophosphazenes) with amino functional groups exhibit reversible sol–gel transitions at temperatures near those of the human body, when in aqueous solution. These polymers form a sol at lower temperatures, and become gels at higher temperatures. Also, these polymer solutions have been found to behave generally like Newtonian fluids in the sol state, but appear to exhibit pseudoplastic qualities in the gel state. The polymers possessing depsipeptide ethyl esters (ethyl‐2‐(O‐glycyl)glycolate) as a side group tend to exhibit much higher degradation rates under physiological conditions than do those which lack the depsipeptide ethyl ester group. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci 120:998–1005, 2011     

Preparation and aqueous solution behavior of a ph‐responsive branched copolymer based on 2‐(diethylamino)ethyl methacrylate

pH‐Responsive amphiphilic branched copolymers were prepared from poly(ethylene glycol) methyl ether methacrylate (PEGMA), 2‐(diethylamino)ethyl methacrylate (DEAEMA), 2‐(tert‐butylamino)ethyl methacrylate (tBAEMA), and ethylene glycol dimethacrylate (EGDMA) utilizing a thiol‐modified free radical polymerization. The molecular structures of copolymers were confirmed by proton nuclear magnetic resonance spectroscopy (¹H NMR) and triple‐detection gel permeation chromatography (tri‐GPC). The aqueous solution behaviors of the obtained copolymers were investigated by dynamic light scattering (DLS). The DLS data showed that about 16 nm polymer particles comprising of hydrophobic poly(tert‐butylamino)ethyl methacrylate (PtBAEMA) and poly(diethylaminoethyl methacrylate (PDEAEMA) core, hydrophilic PEGMA corona were formed above pH 8. With the decrease of pH from 8 to 6, a dramatic increase in the hydrodynamic radius of polymer particles from 16 nm to 130 nm was observed resulting from the protonation of the PDEAEMA segment. Moreover, in vitro drug release behaviors of the resulting polymer assemblies at different pH values were also investigated to evaluate their potential as sustained release drug carriers. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42183.     

Photocatalytic Activity of Titania/Polydicyclopentadiene PolyHIPE Composites

Macroporous polymer composites with photocatalytic activity are prepared by the polymerization of surface modified TiO₂ nanoparticle stabilized high internal phase emulsions. Poly(ethylene glycol‐b‐propylene glycol‐b‐ethylene glycol) triblock copolymer is used to synthesize surface modified TiO₂ anatase via a sol–gel method. Macroporous composites are obtained by the ring opening metathesis polymerization of dicyclopentadiene within the particle‐stabilized high internal phase emulsion templates. Photocatalytic activity of the resulting macroporous polymer composites is described by the kinetic data of the heterogeneous photocatalytic degradation reaction of 4‐nitrophenol.