PEG Segment Length Research Articles

Novel non-fluorinated surfactants for emulsion polymerization of fluorinated monomers

In order to replace toxic fluorinated surfactants such as PFOA and GenX, herein we report a series of non-fluorinated surfactants (NFS) for the emulsion polymerization of fluorinated monomers. The surfactant is a statistic copolymer synthesized from free radical polymerization of poly(ethylene oxide) methacrylate (PEGMA) as hydrophilic monomer with methyl methacrylate (MMA) or tert-butyl methacrylate (TBMA) as hydrophobic comonomer. With properly designed hydrophile lipophile balance (HLB), monomer ratio, and the length of PEG segments, the polymeric NFS form unimolecular micelles in water, which facilitates the emulsion polymerization of fluorinated monomers including vinyl difluoride (VDF) where the solid content of emulsion can be higher than 25 wt% without the occurrence of significant coagulation. The optimized loading ratio of NFS is as low as 88 ppm which is ten times lower than that of fluorinated surfactants. The results demonstrate that the statistic copolymers construct unimolecular micelles to be powerful NFS for the emulsion polymerization of fluorinated monomers.

An AIE polymer prepared via aldehyde-hydrazine step polymerization and the application in Cu2+ and S2− detection

Herein we reported the synthesis of a novel amphiphilic AIE (aggregation-induced emission) polymer with salicylaldehyde azine (SA) moieties and PEG segments in the backbone via the aldehyde-hydrazine step polymerization. The polymer can self-assemble into stable micelles in water at ambient temperature and display intense orange fluorescence because of the aggregation of SA moieties in the core. Moreover, the polymer was found to be thermoresponsive with a relatively high LCST (lower critical solution temperature) and the LCST can be tuned via the chain length of PEG segments. The polymer micelles formed at ambient temperature can serve as a turn-off fluorescent probe for the selective detection of Cu2+ in aqueous media with a low detection limit of 53 nM. The fluorescence of polymer can be completely quenched by Cu2+ and the formed polymer-Cu2+ complex can be used as a turn-on fluorescent probe for the selective detection of S2− with a detection limit of 0.24 μM. The polymer is expected as a useful fluorescent probe for the selective detection of Cu2+ and S2− in environmental field.

Effect of Poly(ethylene glycol) Crystallization on Ionic Conduction and Dielectric Response of Imidazolium-Based Copolyester Ionomers

A molecular-level understanding of ion and polymer dynamics in imidazolium–poly(ethylene glycol) (PEG) copolyester ionomers having different counteranions [PF6– vs (CF3SO2)2N–], alkylene spacer len...

Renewable-based poly((ether)ester)s from 2,5-furandicarboxylic acid

Abstract Polymers based on the renewable monomer 2,5-furandicarboxylic acid (FDCA) have witnessing an incessant growth in recent years, essentially motivated by their unique features and the current concerns about sustainability and environmental issues. However, to date, research has been mainly focused on FDCA-polyesters synthesis, while synthetic routes to afford poly((ether)ester)s remained unexplored until the present study, despite their inherent value. Herein, fully renewable-based poly((ether)ester)s from 2,5-furandicarboxylic acid, poly(ethylene glycol) (PEG) and isosorbide were straightforward synthesised by polycondensation reactions. Interestingly, these materials showed better or comparable thermal properties (e.g. glass transition temperature) than their fossil based counterparts, which can be simply tuned by changing the chain length of PEG segments and also by incorporating (or not) rigid isosorbide moieties. The ensuing products were characterised in detail by means of ATR FTIR, 1H NMR, TGA and DSC.

Stereocomplexation of PLL/PDL–PEG–PDL blends: Effects of blend morphology on film toughness

Polylactide (PL) finds its use in a wide variety of applications ranging from medical devices to engineering plastics. However, the use of PL is limited to certain applications due to its brittle characteristic and low heat distortion temperature, which indicate its poor mechanical and thermal properties, respectively. This present work demonstrated the toughening of PL by stereocomplexation adopting poly(d-lactide)–poly(ethylene glycol)–poly(d-lactide) (PDL–PEG–PDL) copolymers with various PDL segment length. The DSC results showed that the complete stereocomplexation was reached when 40wt% copolymer was blended with poly(l-lactide) (PLL). In addition, the crystallization of PEG was interrupted and, thus, prohibited by either adding PDL or PLL in the system. AFM images showed that, for the first time, the stereocomplex crystallites (Sc-crystallites) formed by the enantiomer pairs were dispersed in a continuous amorphous phase of PL and the non-crystallizing PEG. The increase of PDL segment length in the copolymer leaded to the increase of the Sc-crystallite size, which, consequently, resulted in the increase of the tensile strength of the blended-films. Elongation at break of the films was found to rely on the determined amorphous area. To maximize the toughness of the films, the specific ratio of PDL and PEG segment length in the copolymer must be achieved to provide the optimum balance between Sc-crystallite size and % amorphous area.

Investigation of poly(lactide) stereocomplexation between linear poly(L‐lactide) and PDLA‐PEG‐PDLA tri‐block copolymer

AbstractIn this study, stereocomplexed poly(lactide) (PLA) was investigated by blending linear poly(l‐lactide) (PLLA) and tri‐block copolymer poly(d‐lactide) − (polyethylene glycol) − poly(d‐lactide) (PDLA‐PEG‐PDLA). Synthesized PDLA‐PEG‐PDLA tri‐block copolymers with different PEG and PDLA segment lengths were studied and their influences on the degree of sterecomplexation and non‐isothermal crystallization behaviour of the PLLA/PDLA‐PEG‐PDLA blend were examined in detail by DSC, XRD and polarized optical microscopy. A full stereocomplexation between PLLA and PDLA‐PEG4k‐PDLA200 could be formed when the L/D ratio ranged from 7/3 to 5/5 without the presence of PLA homocrystals. The segmental mobility and length of both PEG and PDLA are the dominating factors in the critical D/L ratio to achieve full stereocomplexation and also for nucleation and spherulite growth during the non‐isothermal crystallization process. For fixed PEG segmental length, the stereocomplexed PLA formed showed first an increasing and then a decreasing melting temperature with increasing PDLA segments due to their intrinsic stiff mobility. Furthermore, the effect of PEG segmental mobility on PLA stereocomplexation was investigated. The results clearly showed that the crystallization temperature and melting temperature of stereocomplexed‐PLA kept increasing with increasing PEG segmental length, which was due to PEG soft mobility in the tri‐block copolymers. However, PEG was not favourable for nucleation but could facilitate the spherulite growth rate. Both the PDLA and PEG segmental lengths in the tri‐block copolymers affect the crystallinity of stereocomplexed‐PLA and the stereocomplexation formation process; they have a different influence on blends prepared by solution casting or the melting method. © 2015 Society of Chemical Industry

Thermodynamics for the Interaction of PEG-PLL Copolymers with DNA

One focus of our research is to select polycations to deliver oligonucleotides into the cell for the control of gene expression. In this work, we report on the interaction of poly(ethylene glycol)-b-poly-L-lysine (PEG-PLL) copolymer with a variety of DNA molecules. Specifically, three PEG-PLL copolymers with similar PEG segment but different length of the PLL chains were used to interact with DNA duplexes as a function of duplex length. A combination of spectroscopic and calorimetric techniques was used to investigate the unfolding of both DNA molecules and polycation-DNA complexes, and to determine their thermodynamic binding profiles. The resulting polycation-DNA complexes were stable in aqueous solution at room temperature. The binding of each copolymer to DNA stabilized the helix-coil transition of all DNA molecules, yielding binding affinities of ∼104 M-1, which were lowered by the increase in salt concentration. However, binding affinities of 105 were obtained with the ethhidium bromide displacement essay. Isothermal titration calorimetric experiments yielded negligible heats of interaction. Therefore, the favorable formation of the copolymer-DNA complexes is entropy driven which was rationalized in terms of the release of both counterions and water molecules upon complex formation. In summary, polycation binding to DNA was found to be electrostatic in nature, i.e., the positively charged lysine groups formed ion pairs with the negatively charged phosphate groups of DNA. Supported by Grant MCB-1122029 from the National Science Foundation.

Controlled synthesis of β-sheet polymers based on side-chain amyloidogenic short peptide segmentsviaRAFT polymerization

A strategy was developed for the controlled synthesis of side-chain peptide containing pH-responsive polymers with an antiparallel β-sheet motif, which was independent of solvent polarity, PEGylation of homopolymers, the block length of PEG or peptidic segments in the block copolymer and temperature.

Improvement of the antifouling properties of poly (lactic acid) hollow fiber membranes with poly (lactic acid)–polyethylene glycol–poly (lactic acid) copolymers

Poly (lactic acid) hollow fiber membranes with poly (lactic acid)–polyethylene glycol–poly (lactic acid) (PLA–PEG–PLA) triblock copolymers were synthesized using different molecular weight PEG segments, and were used as hydrophilic copolymers for the preparation of PLA/PLA–PEG–PLA blend hollow fiber membranes. The effects of the addition of PLA–PEG–PLA copolymers with different PEG segment lengths on the membrane morphology, hydrophobicity, and filtration performance were studied. Fouling experiments performed using BSA indicated that PLA–PEG–PLA copolymers with longer PEG segment lengths were more effective in improving the antifouling properties of the hollow fiber membranes, because of the higher retention of the synthesized copolymer additive in the membrane.

Target-Specific Cellular Uptake of Taxol-Loaded Heparin-PEG-Folate Nanoparticles

To enhance site-specific intracellular delivery against folate receptor, heparin-PEG-folate (H-PEG-F) containing succinylated-heparin conjugated with folate via PEG 1000/3000 spacers has been prepared. Due to covalent strategy, H-PEG-F displays amphiphilic property, which is capable of entrapping a hydrophobic agent, like taxol, to form heparin-PEG-folate-taxol nanoparticles (H-PEG-F-T NPs) in aqueous solution. Hydrophobic agents can be entrapped within the core, while the H-PEG-F conjugates can stabilize the nanoparticles with exposing folate moieties on the surface. The structure of carrier and naoparticles has been characterized by(1)H NMR, and the content of folate and taxol has been quantitatively analyzed by UV method. The morphology and size of H-PEG-F-T NPs have been measured by field emission scanning electron microscopy (FESEM) and dynamic lighting scatter (DLS). All the NPs are in spherical shape and the sizes are less than 200 nm. The sizes of the NPs increases with increasing PEG segment length. By employing the flow cytomery method, the extent of cellular uptake has been comparatively evaluated under various conditions. The results of cellular uptake demonstrate that the cellular uptake of the carrier and the NPs is exceedingly higher for KB-3-1 cells (folate receptor overexpressing cell line) than for A549 cells (folate receptor deficiency cell line); H-PEG-F-T NPs show far greater extent of cellular uptake than that of H-PEG-F conjugates against A549 cells; when the content of folate is fixed at the same value, the extent of cellular uptake for the carrier and NPs ascends with the increase of PEG chain length against KB-3-1 cells. It suggests folate-receptor-mediated endocytosis and formation of nanoparticle and spacer length are considered to coaffect the cellular uptake efficiency of H-PEG-F-T NPs and H-PEG-F conjugates. Flow cytometry analysis depicts that KB-3-1 cells treated with H-PEG-F-T are arrested in the G(2)/M phase of the cell cycle, which states the similar inhibition mechanism as taxol. The strategy based on the formation of H-PEG-F-T NPs could be potentially applied for cancer cell targeted delivery of various therapeutic agents.

Block Copolymer ‘Stealth’ Nanoparticles for Chemotherapy: Interactions with Blood Cells In Vitro

AbstractPassive targeting is one of the approaches to reduce the side effects in intravenous chemotherapeutic administration. This is usually achieved by using so‐called ‘stealth’ particles as carriers, such that the particles can avoid uptake by cells of the reticulo endothelial system (RES) and thus enhance their blood lifetime. To date, there have been no studies of the contribution of various factors to the uptake of particles by the RES, although there is general agreement that a hydrophilic particle surface is helpful. In this study, data is presented on the effect of particle size and surface chemistry on the uptake by monocyte cell lines, as well as by cells in whole blood. Block copolymers of hydrophilic poly(ethylene glycol) (PEG) and the hydrophobic poly(L‐lactide) (PLA) have been used to study surface concentration and conformation effects. It is found that diblock copolymers, in general, show the best stealth characteristics, although triblocks with PEG segment lengths above a certain value are also comparable. It is also found that the uptake goes through a minimum with respect to particle size. For the first time, a method is presented to evaluate the relative uptake efficiency of various types of blood cells, using flow cytometry. The observations are related to structural features found on the polymers.

Poly(ester urethane)s Consisting of Poly[(R)-3-hydroxybutyrate] and Poly(ethylene glycol) as Candidate Biomaterials: Characterization and Mechanical Property Study

Poly(ester urethane)s with poly[(R)-3-hydroxybutyrate] (PHB) as the hard and hydrophobic segment and poly(ethylene glycol) (PEG) as the soft and hydrophilic segment were synthesized from telechelic hydroxylated PHB (PHB-diol) and PEG using 1,6-hexamethylene diisocyanate as a nontoxic coupling reagent. Their chemical structures and molecular characteristics were studied by gel permeation chromatography, 1H NMR, and Fourier transform infrared spectroscopy. Results of differential scanning calorimetry and X-ray diffraction indicated that the PHB segment and PEG segment in the poly(ester urethane)s formed separate crystalline phases with lower crystallinity and a lower melting point than those of their corresponding precursors, except no PHB crystalline phase was observed in those with a relatively low PHB fraction. Thermogravimetric analysis showed that the poly(ester urethane)s had better thermal stability than their precursors. The segment compositions were calculated from the two-step thermal decomposition profiles, which were in good agreement with those obtained from 1H NMR. Water contact angle measurement and water swelling analysis revealed that both surface hydrophilicity and bulk hydrophilicity of the poly(ester urethane)s were enhanced by incorporating the PEG segment into PHB polymer chains. The mechanical properties of the poly(ester urethane)s were also assessed by tensile strength measurement. It was found that the poly(ester urethane)s were ductile, while natural source PHB is brittle. Young's modulus and the stress at break increased with increasing PHB segment length or PEG segment length, whereas the strain at break increased with increasing PEG segment length or decreasing PHB segment length.

In vitro/in vivo correlation for 14C-methylated lysozyme release from poly(ether-ester) microspheres.

The purpose of this study was to obtain an in vitro/in vivo correlation for the sustained release of a protein from poly(ethylene glycol) terephthalate (PEGT)/poly(butylene terephthalate) (PBT) microspheres. Radiolabeled lysozyme was encapsulated in PEGT/PBT microspheres via a water-in-oil-in-water emulsion. Three microsphere formulations varying in copolymer composition were administered subcutaneously to rats. The blood plasma was analyzed for radioactivity content representing released lysozyme at various time points post-dose. The in vitro release was studied in phosphate-buffered saline. The encapsulation efficiency, calculated from the radioactivity in the outer water phase of the emulsion, varied from 60-87%. Depending on the PEG segment length and wt% PEGT, the lysozyme was released completely in vitro within 14 to 28 days without initial burst. 14C-methylated lysozyme could be detected in the plasma over the same time courses. The in vitro/in vivo correlation coefficients obtained from point-to-point analysis were greater than 0.96 for all microsphere formulations. In addition, less then 10% of administered radioactivity remained at dose site at 28 days for the microsphere formulations, indicating no notable retention of the protein at the injection site. The in vitro release in phosphate-buffered saline and the in vivo release in rats showed an excellent congruence independent of the release rate of 14C-methylated lysozyme from PEGT/PBT microspheres.

Biodegradable poly(ether-ester) multiblock copolymers for controlled release applications.

Multiblock poly(ether-ester)s based on poly(ethylene glycol), butylene terephthalate, and butylene succinate units were synthesized by a two-step melt polycondensation reaction, with the aim of developing a new series of degradable polymers for controlled release applications. The copolymers were characterized with respect to their composition (NMR), thermal properties (DSC), and swelling. The main focus was on the degradation kinetics and release properties of the copolymers. The crystallinity and swelling could be tailored by the PEG segment length and the ratio of the building units. With increasing mol fraction succinate in the hard segment, the swelling increased. The in vitro degradation was found to occur by molecular weight decrease and mass loss. Substitution of the aromatic terephthalate units by aliphatic succinate units increased the degradation rate of the copolymers. Polymers with PEG segments of 1000 kg/mol showed a more pronounced degradation than copolymers containing shorter and longer PEG segments. Model proteins were successfully incorporated and released from the poly(ether-ester) films. Depending on the size of the protein, the release mechanism was based on diffusion of the protein and degradation of the matrix.

Isothermal titration calorimetric studies of alkyl phenol ethoxylate surfactants in aqueous solutions

Two commercially available alkyl phenol ethoxylates (APEs), i.e. octyl phenol ethoxylate (Triton X-series) and nonyl phenol ethoxylate (Tergital NP-series), were studied at different temperatures using the isothermal titration calorimetric (ITC) technique. Both the critical micelle concentration (CMC) and the thermodynamic parameters associated with the surfactant micellization were determined. Increasing the length of hydrophilic PEG segments produces a higher CMC and a larger micellization enthalpy. Increasing the size of the hydrophobic alkyl segments leads to a sharp decrease in the CMC. With increasing temperatures, both the CMC and the micellization enthalpy decrease. The thermodynamic parameters revealed that the micellization of APE surfactant is an entropy driven process. Scaling relationships between the lengths of the PEG segments and CMC or micellization enthalpy were developed, i.e. CMC=0.0335N−0.0171; ΔHm=6.5ln(N)−6.2 for Triton X-series, and CMC=0.0082N−0.0068; ΔHm=5.3ln(N)−3.8 for Tergital NP-series, where N represents the number of the oxyethylene repeat units in the surfactant molecules. The thermodynamic parameters obtained from ITC were compared with those determined using the van’t Hoff analysis.

Synthesis and properties of poly(L‐lactide)‐Poly(Ethylene glycol) multiblock copolymers by coupling triblock copolymers

AbstractA series of multiblock copolymers of PLLA/PEG(PLE) with high molecular weight were synthesized by coupling PLLA‐PEG‐PLLA triblock copolymers with succinic anhydride in the presence of N‐dimethylaminopyridine(DMAP) and dicyclohexylcarbodimide (DCC). The results of the viscometry measurement, GPC and 1H NMR, elucidated that multiblock PLE copolymers with high content of short PEG segments had been successfully obtained. The thermal properties and the crystallinity were investigated by DSC and X‐ray diffraction. When LA/EG molar ratio and the length of PEG segments were the same in both multiblock and triblock copolymers, multiblock copolymers were less crystalline than the corresponding triblock ones. Mechanical testing showed that multiblock copolymers had relatively high tensile strength and large elongation. In a word, the measurements showed that this multiblock PLE copolymers had high content of short PEG segments (Mn = 2000,4000), high molecular weight (Mw∼50 000), high hydrophilicity, and good mechanical properties. The drug (5‐Fluorourecil) release behavior of these PLE multiblock copolymers had been studied in 0.10M pH7.4 phosphate buffer solution (PBS), and the releasing rate could be tailored by adjusting copolymers composition. All of these results indicated that the multiblock PLE copolymers might be useful in medical applications. Copyright © 2003 John Wiley & Sons, Ltd.

Preparation and properties of water‐soluble polyester surfactants. I. Preparation and surface activity of poly(ethylene glycol)‐dimethyl 5‐sulfo‐isophthalate sodium salt polyester surfactants

AbstractThe reaction of poly(ethylene glycol) (PEG, number‐average molecular weight Mn = 400‐2000) and dimethyl 5‐sulfoisophthalate sodium salt (SIPM) synthesized a series of anionic polymeric surfactants having a range of molecular weights. 1H‐NMR, FTIR, and elemental analysis were employed to characterize the structures of these compounds. Also, the influences of the PEG segment lengths of PEG/SIPM copolymers on the surface tension, foaming properties, wetting power, and dispersant properties were investigated. The experimental results indicated that the solution that contained the PEG/SIPM copolymer surfactants exhibited excellent surface‐active properties. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2727–2731, 2002

Thermogravimetric investigation of two classes of block copolymers based on poly(lactic-glycolic acid) and poly(ε-caprolactone) or poly(ethylene glycol)

The thermogravimetric analysis (TGA) of two classes of multi-block copolymers based on poly( d, l-lactic-glycolic acid) (PLGA) and diol-terminated poly(ε-caprolactone) (PCDT) or poly(ethylene glycol) (PEG) segments is reported. These materials, having the structure of poly(ester-carbonate)s, were synthesized by a chain extension reaction. The influence of the length of PCDT or PEG segments and of the molar ratio of d, l-lactic acid (LA) and glycolic acid (GA) residues on thermal stability in air and nitrogen atmosphere has been investigated. For comparison purposes the degradation behaviour of starting oligomers was also studied. TGA under nitrogen shows two degradation processes that can be ascribed to the PLGA and PCDT or PEG segments, respectively. In addition, the thermal stability increases with the LA content in the PLGA blocks. In the tests run under air two degradation steps have also been observed, though the former occurs in general at higher temperatures.

Thermally switchable polyrotaxane as a model of stimuli‐responsive supramolecules for nano‐scale devices

AbstractA polyrotaxane consisting of many β‐cyclodextrins (β‐CDs) and a triblock copolymer of poly(ethylene glycol) (PEG) and poly(propylene glycol) (PPG) capped with bulky end‐groups was synthesized as a model of stimuli‐responsive supramolecules for nanoscale devices. The polyrotaxane was reversibly soluble‐insoluble in water in response to temperature. This was achieved through the assembled and dispersed states of β‐CDs along the block copolymer. It is considered that intermolecular hydrogen bondings of β‐CDs, as well as the PEG segment length of the copoloymer, are predominant factors for regulating such thermally switchable behavior of the polyrotaxane.

Flowable networks as DNA sequencing media in capillary columns.

A novel class of materials that self-assemble in water into equilibrium network structures with a well-defined mesh size consist of polyethylene glycols (PEG's) end-capped with micelle-forming fluorocarbon tails. These micellar systems form flowable aqueous gel-like networks that permit electrophoretic DNA sequencing in capillary columns. The gels have unusual rheological properties, including network breakdown under shear, resulting in plug flow that allows columns refill with complete ejection of byproducts of the previous sequencing analysis. In this system, DNA fragment electrophoretic mobilities are unaffected by the hydrophobicity of the polymer tails. Low molecular weight (M) PEG chains (M 8000) show catastrophic resolution loss for DNA fragments larger than 100 bases due to band broadening. For a longer PEG segment (M 35000) separating the end groups, band broadening occurs for DNA fragments larger than 300 bases, implying that the PEG segment length controls the mesh size in the equilibrium network structure. Optimum sequencing results were obtained from a 6% solution of a 1:1 mixture of C6F13 end-capped- and C8F17 end-capped PEG 35,000. The resolution limit of fluorescent-dye-labeled sequencing products in this formulation was 450 bases in 75 microns capillaries at 200 V/cm.