Synthesis and interfacial behaviors of amphiphilic poly(oxypropylene) amidoacids

A series of hydrophobic poly(oxypropylene) (POP)‐backboned and hydrophilic poly(oxyethylene)‐backboned amidoacids and imidoacids were prepared through the reaction of poly(oxyalkylene) diamines and trimellitic anhydride (TMA) under mild conditions. The synthesized copolymers were characterized with nuclear magnetic resonance and Fourier transform infrared. Their ability to lower the water surface tension and toluene/water interfacial tension was measured and correlated with the hydrophobic/hydrophilic balance with multiple sodium carboxylate functionalities. The specific POP2000/TMA copolymers, consisting of a 2000 g/mol POP segment and multiple amidoacid functionalities, enabled the demonstration of a strong surfactant tendency and a critical micelle concentration at 0.1 wt %. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 646–652, 2006     

Synthesis and self‐assembly of tadpole‐shaped organic/inorganic hybrid poly(N‐isopropylacrylamide) containing polyhedral oligomeric silsesquioxane via RAFT polymerization

Aminopropylisobutyl polyhedral oligomeric silsesquioxane (POSS) was used to prepare a POSS‐containing reversible addition‐fragmentation transfer (RAFT) agent. The POSS‐containing RAFT agent was used in the RAFT polymerization of N‐isopropylacrylamide (NIPAM) to produce tadpole‐shaped organic/inorganic hybrid Poly(N‐isopropylacrylamide) (PNIPAM). The results show that the POSS‐containing RAFT agent was an effective chain transfer agent in the RAFT polymerization of NIPAM, and the polymerization kinetics were found to be pseudo‐first‐order behavior. The thermal properties of the organic/inorganic hybrid PNIPAM were also characterized by differential scanning calorimetry. The glass transition temperature (T_g) of the tadpole‐shaped inorganic/organic hybrid PNIPAM was enhanced by POSS molecule. The self‐assembly behavior of the tadpole‐shaped inorganic/organic hybrid PNIPAM was investigated by atomic force microscopy and dynamic light scattering. The results show the core‐shell nanostructured micelles with a uniform diameter. The diameter of the micelle increases with the molecular weight of the hybrid PNIPAM. Surprisingly, the micelle of the tadpole‐shaped inorganic/organic hybrid PNIPAM with low molecular weight has a much bigger and more compact core than that with high molecular weight. © Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7049–7061, 2008     

Fabrication and characterization of UV‐crosslinkable thermoresponsive composite fibers with magnetic properties

Crosslinking magnetic thermoresponsive composite (MTC) fiber mats were fabricated by electrospinning process and followed by UV curing. Thermoresponsive poly‐(N‐isopropylacrylamide) (PNIPAAm) and magnetic Fe₃O₄ were firstly synthesized by redox‐initiated polymerization and co‐precipitation, respectively. A crosslinking agent (dipentaerythritol hexylacrylate) and photoinitiator for providing crosslinking ability were then mixed with PNIPAAm and Fe₃O₄ in ethanol as the electrospinning solution. After electrospinning and subsequent UV irradiation, the MTC fiber mats were thus obtained. Thermoresponsivity of the MTC fibers was measured by both DSC and swelling test. MTC fiber mat exhibited better water‐absorption capability and thermoresponsivity than corresponding film. Morphological analysis was observed by SEM and TEM, and the magnetic property was measured by SQUID. The thermoresponsive magnetic behavior of MTC fiber mat in water was observed under various temperatures and magnetic fields. Vitamin B₁₂ used as a model drug was loaded in the MTC fiber mats and the drug‐release behavior was then studied. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2152–2162     

Folate receptor-mediated gene delivery using folate-poly(ethylene glycol)-poly(L-lysine) conjugate

For efficient receptor-mediated gene transfection, a new and simple formulation method based on using PEI and FOLPEGPLL conjugate was presented. Luciferase plasmid DNA and PEI were complexed to form slightly positive-charged nanoparticles, onto which FOL-PEG-PLL conjugate was surface coated. With increasing the coating amount of FOL-PEG-PLL conjugate, the FOL-PEG-PLL/PEI/DNA complexes exhibited increased surface zeta-potential values with concomitantly increased diameters, indicating that the PLL part was physically anchored on the surface of preformed PEI/DNA complexes with FOL moieties being exposed on the outside. The formulated complexes exhibited a considerably higher transfection efficiency against FOL receptor over-expressing KB cells than FOL receptor deficient A549 cells. This was caused by an enhanced cellular uptake of the resultant complexes via a receptor-mediated endocytosis process. The formulated complexes showed a higher gene expression level, even in the presence of serum, than the PEI/DNA or Lipofectamine/DNA complexes. This was attributed to the PEG chains present on the surface of complexes that could work as a protective shield layer against aggregation caused by non-specific protein adsorption. The FOL-PEG-PLL/PEI/DNA complexes also demonstrated better cell viability than the PEI/DNA complexes.(1)H NMR spectrum of FOL-PEG-PLL conjugate.     

Exploring the synthesis and impact of end‐functional poly(3‐hexylthiophene)

In recent years, end‐functional poly(3‐hexylthiophene) (P3HT) has proven to be instrumental in the continued development and innovation within the broad conjugated polymer arena, enabling a variety of applications, particularly in organic electronics. The availability of P3HT with controlled molecular weights, low polydispersity, and importantly, a wide range of reactive end‐groups not only serves as a key building block for the preparation of conjugated block copolymers but also facilitates the development of hybrid nanocomposite materials via inorganic surface modification strategies. This Highlight focuses on the synthetic approaches to end‐functional P3HT and the impact of these systems in emerging technologies. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 831–841     

Synthesis and Characterization of Cross‐Linked Poly(p‐phenylene ethynylene)s

Summary: Conjugated poly(p‐phenylene ethynylene) networks with interesting optoelectronic properties were synthesized by the palladium‐catalyzed polycondensation of 2,5‐diiodo‐4‐[(2‐ethylhexyl)oxy]methoxybenzene, and 1,4‐diethynyl‐2,5‐bis‐(octyloxy)benzene, with 1,2,4‐tribromobenzene as cross‐linker. The cross‐linker concentration was varied and materials with different cross‐link densities were prepared. The materials were processed into films by simultaneous polymerization and shaping. An alternative approach is to synthesize these cross‐linked polymers in the form of spherical particles, which can be processed from dispersions.

Schematic representation of the cross‐linking process.     

Synthesis and self‐assembly of a chiral alternating sexithiophene–undeca(ethyleneoxy) block copolymer

An oligothiophene/chiral oligo(ethyleneoxy) block copolymer (PolyT6) has been synthesized in which a sexithiophene block alternates with a well‐defined chiral undeca(ethyleneoxy) block. The polymer shows good solubility in chloroform, and ultraviolet–visible studies in this solvent reveal a spectrum similar to that of the chirally substituted monomeric sexithiophene (T6) analogue. The aggregation of PolyT6 occurs in dioxane; however, no helicity is present in this aggregate, in contrast to aggregated T6. This behavior illustrates that although the processability and mechanical robustness of block copolymers may be superior to those of analogous oligomers, the degree of self‐assembled order found in oligomer‐based systems may be lost in the polymers. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1737–1743, 2003     

Synthesis,characterization, and structure–property investigation of conformationally rigid regioisomers of poly(p‐phenylene ethynylene)s

A series of rigid poly(p‐phenylene ethynylene)s ( PPE1 – PPE4 ) with biphenyl‐ ( M1–M3 ) and phenyl‐ ( M4 ) side groups is prepared from appropriately functionalized monomers. Herein, the solution and solid state absorption studies show the polymers have adopted twisted and rigid conformations, as supported by deep HOMO energy levels (?5.76 to ?5.81 eV). The absorption maxima of PPE1–PPE3 are shifted to shorter wavelength (λ_max = 375–381 nm) as compared to linear poly(p‐phenylene ethynylene)s (446 nm), implying a nonplanar conformation. The self‐assembly of polymers into fibers is examined using scanning electron microscopy. The fibers are not observed in PPE4 with short phenyl side group, suggesting the important role of the interplay between rigidity, position, and size of the side chains toward the formation of fibers. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3652–3662     

Properties of a novel thermal sensitive polymer based on poly(vinyl alcohol) and its layer‐by‐layer assembly

Structurally modified poly(vinyl alcohol) (PVA) was prepared as novel thermally sensitive polymers by partially acetalyzing and/or ionizing the commercially available PVA. Their aqueous solutions experience completely reversible polymer aggregation and dissolution above and below the lower critical solution temperature (LCST), respectively. The LCST of a partially acetalyzed PVA (APVA) can be readily controlled by the degree of acetalysis or the molecular weight of the starting PVA. Introduction of a small amount of cationic group onto the APVA backbone increases the LCST obviously, while the LCST is highly sensitive to NaCl concentration. Then APVA and cationic APVA multilayers are assembled on rayon to make a thermal responsive fiber. The atomic force microscopy (AFM) images of the surface reveal the increment of roughness stimulated by temperature. Copyright © 2007 John Wiley & Sons, Ltd.     

Associative block copolymers comprising poly(N‐isopropylacrylamide) and poly(ethylene oxide) end‐functionalized with a fluorophilic or hydrophilic group. Synthesis and aqueous solution properties

A series of block copolymers comprising poly(N‐isopropylacrylamide) (PNIPAM) and poly(ethylene oxide) (PEO) end‐functionalized with a quaternary ammonium group (R_Q) was synthesized by free‐radical polymerization of N‐isopropylacrylamide with well‐defined R_QPEO macroazoinitiators. The radical termination occurred mainly by disproportionation, as confirmed by combining the data from size exclusion chromatography (SEC) and rheology measurements. The copolymers denoted R_QE_xN_y differ in type of the terminal group [F_Q = C₈F₁₇(CH₃)₂N⁺ or M_Q = (CH₃)₃N⁺] and in the length of the PEO (E_x; x = 4, 6, or 10 K) and PNIPAM (N_y; y = 7 or 17–19 K) blocks. The type of the terminal group determined the behavior of the block copolymers in the dilute and semidilute regime. Self‐assembled species formed by both F_Q and M_Q modified block copolymers were detected by static light scattering measurements at 25 °C and above the lower critical solution temperature (LCST). The LCST of the block copolymers depended on the type of the R_Q group and the length of the blocks. F_Q‐modified copolymers form elastic gels below and above the LCST. It was inferred that the F_Q groups and the PNIPAM blocks form segregated microdomains that serve as junctions to maintain a viscoelastic network. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5736–5744, 2004     

Para‐linked and meta‐linked cationic water‐soluble fluorene‐containing poly(aryleneethynylene)s: Conformational changes and their effects on iron–sulfur protein detection

Four para‐linked or meta‐linked cationic water‐soluble fluorene‐containing poly(aryleneethynylene)s (PAEs) were synthesized to investigate the solvent‐induced π‐stacked self‐assembly. These PAE backbones are composed of fluorenylene and phenylene units, which are alternatively linked by ethynylene bonds. UV–vis absorption and photoluminescence spectra were used to study their conformational changes as solvent was gradually changed from MeOH to H₂O. In pure water, with gradually increased meta‐phenylene content (0, 50, and 100%), they underwent a gradual transition process of conformation from disordered aggregate structure to helix structure, which was not compactly folded. Moreover, the polymer with an ammonium‐functionalized side chain on the meta‐phenylene unit appeared to adopt a more incompact or extended helix conformation than the corresponding one without this side chain. Furthermore, the conformational changes of these cationic PAEs in H₂O were used to study their effects on biological detection. Rubredoxin (Rd), a type of anionic iron–sulfur‐based electron transfer protein, was chosen to act as biological analyte in the fluorescence quenching experiments of these polymers. Preliminary results suggest that they all exhibit amplified fluorescence quenching, and that the polymer with more features of helix conformation tends to be quenched by Rd more efficiently. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5424–5437, 2006     

Bioactive mesoglobules of poly(di(ethylene glycol) monomethyl ether methacrylate)–peptide conjugate

This study describes the synthesis and aggregation behavior of thermosensitive poly(di(ethylene glycol) monomethyl ether methacrylate) (P(DEGMA‐ME)) conjugated with the fluorescently labeled pentapeptide glycine‐arginine‐lysine‐phenylalanine‐glycine‐dansyl (GRKFG‐Dns). The GRKFG‐Dns was obtained using Fmoc solid‐phase peptide synthesis and was modified with 2‐bromopropionic acid to initiate an atom transfer radical polymerization of di(ethylene glycol) monomethyl ether methacrylate (DEGMA‐ME). The polymerization led to a well‐defined P(DEGMA‐ME)–GRKFG‐Dns conjugate with a number average molar mass of 108,000 g/mol. The pentapeptide acted as a hydrophilic moiety that increased the phase transition temperature compared to the P(DEGMA‐ME) homopolymer of similar molar mass. The bioconjugate macromolecules aggregated in dilute aqueous solution into spherical particles (mesoglobules). The sizes of aggregates were easily controlled by changing the concentration and heating rate of the P(DEGMA‐ME)‐GRKFG‐Dns solution. The weight average molar masses and sizes of mesoglobules were determined based on light scattering measurements. Enzymatic hydrolysis of the bioconjugate in dilute solution was performed at temperatures below and above the cloud point temperature of the bioconjugate. The peptides were fully accessible to enzymatic digestion even when the macromolecules were aggregated to mesoglobules, indicating that the peptide segments in mesoglobules formed the external shell of the nanoparticles and could be easily released by enzymes. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Mechanism of anation of chromium (III) by L-lysine

The kinetics of L-lysine anation of aquachromium(III) ions have been investigated in the acidity range 5.6 ≤ 10⁵[H⁺] ≤ 31.6 mol dm⁻. The reaction takes place with outer-sphere association between Cr³⁺/CrOH²⁺ and H₂L⁺ (L =⁺HGCH (⁺NH₃)(CO ₂ ^t- ), G being the side chain) followed by transformation of the outer-into an inner-sphere complex by slow interchange. The results are discussed in relation to the data of analogous systems and it is concluded that anation of [Cr(H₂O)₆]^{3 +} follows anI _a path whereas that of [Cr(H₂O)₅OH]_{2 +} follows anI _d path.     

Design,Synthesis and Characterization of A Novel Cationic Polymer Poly(lactic acid-b-L-lysine)

A novel biodegradable block copolymer poly(lactic acid-b-lysine) (PLA-b-PLL) has been synthesized and characterized in this study. This product was synthesized via a five-step reaction: Synthesis of hydroxyl-tailed poly(lactic acid) (PLA) by the ring-opening polymerization (ROP) of D,L-lactide in the presence of stannous octoate (Sn(OCt)₂) as initiator; coupling N-t-butoxycarbonyl-L-phenylalanine to hydroxyl-tailed PLA using dicyclohexylcarbodiimide (DCC) and 4-dimethylaminopyridine (DMAP); the amino-tailed PLA was obtained through de-protection of the Boc-protective group in trifluoroacetic acid (TFA) solution; and then ring-opening polymerization of N ^ε -(Z)-lysine-N-carboxyanhydride (NCA) using the amino-tailed PLA as macro-initiator; finally removal of the Cbz-protective group of PLA-b-poly(N ^ε -(Z)-L-lysine) (PLA-b-PLL(Z) in a mixed hydrobromic acid/acetic acid solution to give the target copolymer. The characterization of this copolymer and its precursors were performed by ¹H-NMR, FTIR and GPC. The block copolymer PLA-b-PLL, combining the characteristics of an aliphatic polyester and poly(amino acids), could be of potential interest in a variety of medical applications, such as the fields of targeted drug delivery and gene delivery systems.     

Biocompatibility evaluation of self‐assembled micelles prepared from poly(lactide‐co‐glycolide)‐poly(ethylene glycol) diblock copolymers

In this work, a series of PLGA‐PEG diblock copolymers were synthesized by ring‐opening polymerization of L‐lactide and glycolide using mPEG as macroinitiator and stannous octoate as catalyst. Spherical micelles were obtained from the various copolymers by using co‐solvent evaporation method. The biocompatibility of micelles was evaluated with the aim of assessing their potential in the development of drug delivery systems. Various aspects of biocompatibility were considered, including MTT assay, agar diffusion test, release of cytokines, hemolytic test, dynamic clotting time, protein adsorption in vitro, and zebrafish embryonic compatibility in vivo. The combined results revealed that the micelles present good cytocompatibility and hemocompatibility in vitro. Moreover, the cumulative effects of micelles throughout embryos developing stages have no toxicity in vivo. It is thus concluded that micelles prepared from PLGA‐PEG copolymers present good biocompatibility as potential drug carrier.     

Crystallization kinetics of crosslinkable polymer complexes of novolac resin and poly(ethylene oxide)

Results of a study on the isothermal crystallization and thermal behavior of both uncured and hexamine-cured novolac/poly(ethylene oxide) (PEO) complexes are reported. The crystallization behavior of PEO in complexes is strongly influenced by factors such as composition, crystallization temperature, complexation, and crosslinking. The time dependence of the relative degree of crystallinity at high conversion deviated from the Avrami equation. The cured complexes exhibited an obvious two-stage crystallization (primary crystallization and crystal perfection), and this was more evident at higher crystallization temperature and high PEO-content. The addition of a noncrystallizable component into PEO caused a depression of both the overall crystallization rate and the melting temperature. In general, complexation and curing resulted in an increase in the overall crystallization rate. Complexation and curing are beneficial to the nucleation of PEO. Additionally, curing led to changes of the nucleation mechanism. Experimental data on the overall kinetic rate constant K_n were analyzed by means of the nucleation and crystal growth theory. For uncured complexes, the surface free energy of folding, σ_e, increased with increasing novolac content, whereas for cured complexes, σ_e displayed a maximum with the variation of composition. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2726–2736, 1999     

Copolymer of star poly(epsilon‐caprolactone) and polyglycidols as potential carriers for hydrophobic drugs

Amphiphilic star shape poly(ε‐caprolactone)‐b‐hyperbranched polyglycidol (sPCL‐HPG) were synthesized and used to investigate micell formation and to encapsulate hydrophobic drugs. The synthesis of sPCL‐HPG copolymers was carried out by using sPCL as macroinitiator for the ensuing of hypergrafting reaction with glycidols. ¹H‐NMR and FTIR were used to characterize sPCL‐b‐HPG structures. The self‐assembled structure of the sPCL‐HPG was characterized by scanning electronic microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM). The size and size dispersities of micelles were measured by dynamic light scattering DLS. Critical micelle concentration (CMC) was determined using pyrene as fluorescent probe. Hydrophobic methyl red was encapsulated in sPCL‐HPG micelles to illustrate hydrophobic drug loading. The copolymer micelles were used to enhance paclitaxel solubility. The results showed that hydrophobic drugs could be encapsulated in the sPCL‐HPG micelles. The paclitaxel solubility in the micelles of 5 wt% of sPCL23‐HPG170 got to 168 µg/ml. sPCL‐HPG, which have biodegrability and hydrophobicity at PCL part and smaller size of HPG fragments while maintaining the total repeating units of glycidols, provide an alternative choice of carriers for poorly soluble drugs. Copyright © 2011 John Wiley & Sons, Ltd.     

Synthesis and characterization of amphiphilic block copolymer of polyphosphoester and poly(L‐lactic acid)

Aliphatic polyesters and polyphosphoesters (PPEs) have received much interest in medical applications due to their favorable biocompatibility and biodegradability. In this work, novel amphiphilic triblock copolymers of PPE and poly(L ‐lactic acid) (PLLA) with various compositions were synthesized and characterized. The blocky structure was confirmed by GPC analyses. These triblock copolymers formed micelles composed of hydrophobic PLLA core and hydrophilic PPE shell in aqueous solution. Critical micellization concentrations of these triblock copolymers were related to the polymer compositions. Incubation of micelles at neutral pH followed by GPC analyses revealed that these polymer micelles were hydrolysized and resulted in decreased molecular weights and small oligomers, whereas its degradation in basic and acid mediums was accelerated. MTT assay also demonstrated the biocompatibility against HEK293 cells. These biodegradable polymers are potential as drug carriers for biomedical application. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6425–6434, 2008     

Synthesis of thermally crosslinkable fluorine‐containing poly(arylene ether ketone)s—II. Propargyl ether terminated poly(arylene ether ketone)s

Novel thermally crosslinkable fluorine‐containing poly(arylene ether ketone)s comprised of 2,3,5, 6‐tetrafluoro‐1,4‐phenylene moiety were synthesized by the termination of polymer chain ends with propargyl ether groups in order to improve solvent resistance. Crosslinking reaction occurred over 250°C through the formation of both chromen ring and polyene structure. This structure change brought about not only the outstanding solvent resistance but also the increase in glass transition temperature (T_g). The cured films also exhibited excellent thermal stability, transparency and hydrophobicity derived from fluorine atoms. Copyright © 2004 John Wiley & Sons, Ltd.