Well‐Defined SiO2@P(EtOx‐stat‐EI) Core–Shell Hybrid Nanoparticles via Sol‐Gel Processes

Positively charged nanoparticles (NPs) are very interesting for biomedical and pharmaceutical applications, such as nonviral gene delivery. Here, the synthesis of SiO₂ nanoparticles with a covalently grafted poly(2‐ethyl‐2‐oxazoline) (PEtOx) shell (SiO₂@PEtOx) is presented. PEtOx with a degree of polymerization of 20 and 38 is synthesized via microwave supported cationic ring‐opening polymerization and subsequently end‐functionalized with a triethoxysilyl linker for subsequent grafting to silica particles with hydrodynamic radii of 7, 31, and 152 nm. The resulting SiO₂@PEtOx particles are characterized by using dynamic light scattering (DLS), transmission electron microscopy (TEM, cryoTEM), and scanning electron microscopy (SEM) to determine changes in particle size. Thermal gravimetrical analysis is used to quantify the amount of polymer on the silica surface. Subsequent in situ transformation of SiO₂@PEtOx particles into SiO₂@P(EtOx‐stat‐EI) (poly(2‐ethyl‐2‐oxazoline‐stat‐ethylene imine) grafted silica particles) under acidic conditions inverts the surface charge from negative to positive according to ζ‐potential measurements. The P(EtOx‐stat‐EI) shell could be used for the deposition of Au NP afterward.

     

Poly(ethylene imine)s as Antimicrobial Agents with Selective Activity

We report the structure–activity relationship in the antimicrobial activity of linear and branched poly(ethylene imine)s (L‐ and B‐PEIs) with a range of molecular weights (MWs) (500–12 000). Both L‐ and B‐PEIs displayed enhanced activity against Staphylococcus aureus over Escherichia coli. Both B‐ and L‐PEIs did not cause any significant permeabilization of E. coli cytoplasmic membrane. L‐PEIs induced depolarization of S. aureus membrane although B‐PEIs did not. The low MW B‐PEIs caused little or no hemolysis while L‐PEIs are hemolytic. The low MW B‐PEIs are less cytotoxic to human HEp‐2 cells than other PEIs. However, they induced significant cell viability reduction after 24 h incubation. The results presented here highlight the interplay between polymer size and structure on activity.

     

Thermoresponsive Poly(2‐oxazine)s

The monomers 2‐methyl‐2‐oxazine (MeOZI), 2‐ethyl‐2‐oxazine (EtOZI), and 2‐n‐propyl‐2‐oxazine (nPropOZI) were synthesized and polymerized via the living cationic ring‐opening polymerization (CROP) under microwave‐assisted conditions. pEtOZI and pnPropOZI were found to be thermoresponsive, exhibiting LCST behavior in water and their cloud point temperatures (T_CP) are lower than for poly(2‐oxazoline)s with similar side chains. However, comparison of poly(2‐oxazine) and poly(2‐oxazoline)s isomers reveals that poly(2‐oxazine)s are more water soluble, indicating that the side chain has a stronger impact on polymer solubility than the main chain. In conclusion, variations of both the side chains and the main chains of the poly(cyclic imino ether)s resulted in a series of distinct homopolymers with tunable T_CP.     

Tuning the Surface of Nanoparticles: Impact of Poly(2‐ethyl‐2‐oxazoline) on Protein Adsorption in Serum and Cellular Uptake

Due to the adsorption of biomolecules, the control of the biodistribution of nanoparticles is still one of the major challenges of nanomedicine. Poly(2‐ethyl‐2‐oxazoline) (PEtOx) for surface modification of nanoparticles is applied and both protein adsorption and cellular uptake of PEtOxylated nanoparticles versus nanoparticles coated with poly(ethylene glycol) (PEG) and non‐coated positively and negatively charged nanoparticles are compared. Therefore, fluorescent poly(organosiloxane) nanoparticles of 15 nm radius are synthesized, which are used as a scaffold for surface modification in a grafting onto approach. With multi‐angle dynamic light scattering, asymmetrical flow field‐flow fractionation, gel electrophoresis, and liquid chromatography‐mass spectrometry, it is demonstrated that protein adsorption on PEtOxylated nanoparticles is extremely low, similar as on PEGylated nanoparticles. Moreover, quantitative microscopy reveals that PEtOxylation significantly reduces the non‐specific cellular uptake, particularly by macrophage‐like cells. Collectively, studies demonstrate that PEtOx is a very effective alternative to PEG for stealth modification of the surface of nanoparticles.

     

Comparative studies on miscibility and phase behavior of linear and star poly(2‐methyl‐2‐oxazoline) blends with poly(vinylidene fluoride)

The comparative studies on the miscibility and phase behavior between the blends of linear and star‐shaped poly(2‐methyl‐2‐oxazoline) with poly(vinylidene fluoride) (PVDF) were carried out in this work. The linear poly(2‐methyl‐2‐oxazoline) was synthesized by the ring opening polymerization of 2‐methyl‐2‐oxazoline in the presence of methyl p‐toluenesulfonate (MeOTs) whereas the star‐shaped poly(2‐methyl‐2‐oxazoline) was synthesized with octa(3‐iodopropyl) polyhedral oligomeric silsesquioxane [(IC₃H₆)₈Si₈O₁₂, OipPOSS] as an octafunctional initiator. The polymers with different topological structures were characterized by means of Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. It is found that the star‐shaped poly(2‐methyl‐2‐oxazoline) was miscible with poly(vinylidene fluoride) (PVDF), which was evidenced by single glass‐transition temperature behavior and the equilibrium melting‐point depression. Nonetheless, the blends of linear poly(2‐methyl‐2‐oxazoline) with PVDF were phase‐separated. The difference in miscibility was ascribed to the topological effect of PMOx macromolecules on the miscibility. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 942–952, 2006     

First aldehyde-functionalized poly(2-oxazoline)s for chemoselective ligation

A protected aldehyde-functionalized 2-oxazoline, 2-[3-(1,3)-dioxolan-2-ylpropyl]-2-oxazoline (DPOx), was synthesized from commercially available compounds in high yields. The polymerization of DPOx with different initiators proceeds via a living ionic mechanism; thus, the polymers were of low polydispersity and the degree of polymerization could be precisely adjusted. Copolymerization with 2-methyl-2-oxazoline gave water-soluble statistical copolymers. Hydrolysis of the homo- and copolymers resulted in well-defined, aldehyde-bearing poly(2-oxazoline)s. The aldehyde side functions reacted quantitatively with an amino-oxy compound to form the corresponding oxime.     

Poly(ether imide) membranes modified with poly(ethylene imine) as potential carriers for epidermal substitutes

Poly(ether imide) (PEI) membranes were modified with a linear low-molecular weight (PETIM_0.6) and a branched high-molecular weight poly(ethylene imine) (PETIM_60). The membrane surfaces became more hydrophilic and the zeta potentials were shifted from negative to positive zeta values after immobilisation of both PETIM. These measurements also indicated the presence of a swollen surface layer in the case of PETIM_60, while a regular structuring of the surface was observed with scanning force microscopy for PETIM_0.6. A human keratinocyte cell line HaCaT was cultured on the different membranes. It was found that HaCaT cell growth was stimulated by PETIM_0.6. Cells reached earlier confluence on this substratum, while their growth was inhibited on a PEI membrane modified with PETIM_60, which makes PEI membranes modified with PETIM_0.6 a promising material for in vitro culture of epidermal transplants.     

Uni‐molecular nanoparticles of poly(2‐oxazoline) showing tunable thermoresponsive behaviors

Herein, cylindrical molecular bottlebrushes grafted with poly(2‐oxazoline) (POx) as a shaped tunable uni‐molecular nanoparticle were synthesized via the grafting‐onto approach. First, poly(glycidyl methacrylate) (PGMA) backbones with azide pendant units were prepared via reversible addition fragmentation transfer (RAFT) polymerization followed by post‐modification. The degree of polymerization (DP) of the backbones was tuned in a range from 20 to 800. Alkynyl‐terminated POx side chains were synthesized by living cationic ring opening polymerization (LCROP) of 2‐ethyl‐2‐oxazoline (EtOx) and 2‐methyl‐2‐oxazoline (MeOx), respectively. The DP of side chains was varied between 20 and 100. Then, the copper‐catalyzed azide‐alkynyl cycloaddition (CuAAC) click chemistry was conducted with a feed ratio of [alkynyl]:[azide] = 1.2:1 to yield a series of brushes. Depending on the DP of side chains, the grafting density ranged between 47 and 85%. The resulting brushlike nanoparticles exhibited shapes of sphere, rod and worm. Aqueous solutions of PEtOx brushes demonstrated a thermoresponsive behavior as a function of the length of backbones and side chains. Surprisingly, it was found that the lower critical solution temperature of PEtOx brushes increased with a length increase of backbones. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 174–183     

Poly(2‐oxazoline) hydrogels crosslinked with aliphatic bis(2‐oxazoline)s: Properties,cytotoxicity, and cell cultivation

A series of hydrogels from 2‐ethyl‐2‐oxazoline and three bis(2‐oxazoline) crosslinkers—1,4‐butylene‐2,2′‐bis(2‐oxazoline), 1,6‐hexamethylene‐2,2′‐bis(2‐oxazoline), and 1,8‐octamethylene‐2,2′‐bis(2‐oxazoline)—are prepared. The hydrogels differ by the length of aliphatic chain of crosslinker and by the percentage of crosslinker (2–10%). The influence of the type and the percentage of the crosslinker on swelling properties, mechanical properties, and state of water is studied. The equilibrium swelling degree in water ranges from 2 to 20. With a proper selection of the crosslinker, Young's modulus can be varied from 10 kPa to almost 100 kPa. To evaluate the potential for medical applications, the cytotoxicity of extracts and the contact toxicity toward murine fibroblasts are measured. The hydrogels with the crosslinker containing a shorter aliphatic exhibit low toxicity toward fibroblast cells. Moreover, the viability and the proliferation of pancreatic β‐cells incubated inside hydrogels for 12 days are analyzed. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1548–1559     

In vitro hemocompatibility and cytotoxicity study of poly(2‐methyl‐2‐oxazoline) for biomedical applications

Since poly(2‐methyl‐2‐oxazolines) (PMeOx) attract high attention for the potential use in drug delivery, cytotoxicity, and hemocompatibility of a set of PMeOxs with molar masses in the range from 2 to 20 kDa are systematically investigated under standardized conditions in terms of molar mass, concentration and time dependency. PMeOx polymers are well tolerated in red blood cell aggregation and hemolysis assays without any damaging effects even at high concentrations up to 80 mg/mL. Only in long term cytotoxicity tests PMeOx polymers moderately influence cell viability in a time, concentration, and molar mass dependent manner. Referring to these results it can be concluded that PEtOx could be promising nonionic hydrophilic polymers for many biomedical applications without any cyto‐ and hemotoxic effects at typically used therapeutic doses. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Synthesis,characterization, and degradation of poly(ethylene‐b‐ε‐caprolactone) diblock copolymer

Poly(ethylene‐b‐ε‐caprolactone) (PE‐b‐PCL) diblock copolymers were synthesized by ring‐opening polymerization (ROP) of ε‐caprolactone (CL) with α‐hydroxyl‐ω‐methyl polyethylene (PE‐OH) as a macroinitiator and ammonium decamolybdate (NH₄)₈[Mo₁₀O₃₄] as a catalyst. Polymerization was conducted in bulk (130–150°C) with high yield (87–97%). Block copolymers with different compositions were obtained and characterized by ¹H and ¹³C NMR, MALDI‐TOF, SAXS, and DSC. End‐group analysis by NMR and MALDI‐TOF indicates the formation of α‐hydroxyl‐ω‐methyl PE‐b‐PCL. The PE‐b‐PCL degradation was studied using thermogravimetric analysis (TGA) and alkaline hydrolysis. The PCL block was hydrolyzed by NaOH (4M), without any effect on the PE segment. Copyright © 2009 John Wiley & Sons, Ltd.     

Toward the design of LPEI containing block copolymers: Improved synthesis protocol,selective hydrolysis,and detailed characterization

The synthesis of poly(2‐ethyl‐2‐oxazoline)‐b‐linear poly(ethylenimine) (PEtOx‐b‐LPEI) copolymers by selective basic hydrolysis of PEtOx‐b‐poly(2‐H‐2‐oxazoline) (PEtOx‐b‐PHOx) is described. For this purpose, an easy method for the preparation of the 2‐H‐2‐oxazoline (HOx) monomer was developed. Based on the microwave‐assisted polymerization kinetics for this monomer, PEtOx‐b‐PHOx copolymers were prepared. Subsequently, the block copolymers were selectively hydrolyzed to PEtOx‐b‐LPEI under basic conditions. The success of the polymerizations and subsequent post‐polymerization reactions was demonstrated by ¹H NMR spectroscopy and MALDI‐TOF‐MS investigations of the obtained polymers. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

聚乙烯胺类修饰萘酰亚胺衍生物的合成、DNA键合行为和活性研究

合成了二乙烯三胺、三乙烯四胺和四乙烯五胺等低分子量聚乙烯胺类修饰的萘酰亚胺衍生物.通过UV-Vis谱、荧光光谱、圆二色谱和热变性试验研究了合成化合物与小牛胸腺DNA的键合行为,同时通过四甲基偶氮唑蓝(MTT)染色法研究了化合物对Bel-7402(人肝癌细胞)、HL-60(白血病细胞)、A549(人肺癌细胞)和Hela(人宫颈癌细胞)等细胞株的体外抗肿瘤活性,化合物NI1对A549细胞显示良好的抑制活性,优于阳性对照顺铂.     

Poly(cyclic imino ether)s Beyond 2‐Substituted‐2‐oxazolines

2‐Oxazolines (2‐OZO) are 5‐membered cyclic imino ethers whose cationic ring‐opening polymerization (CROP) mechanism and resulting polymer properties are extensively studied. However, also 6‐ and 7‐membered cyclic imino ethers can be polymerized via CROP. Together with the much less studied 4‐ and 5‐substituted main‐chain chiral poly(2‐oxazoline)s (P‐2‐OZO), these compounds are interesting monomers to enhance the versatility of (co)poly(cyclic imino ether)s. To emphasize the potential of such alternative cyclic imino ether monomers, we provide an overview on the polymerizations of 2‐oxazine (2‐OZI) and chiral 4‐ and 5‐substituted 2‐OZO as well as of selected properties of the resulting polymers. In addition, the hydrolysis of these polymers into the corresponding poly(alkylene imine)s will be addressed.

     

Thermal,crystallization, mechanical,and rheological characteristics of poly(trimethylene terephthalate)/poly(ethylene terephthalate) blends

Blends of poly(trimethylene terephthalate) (PTT) and poly(ethylene terephthalate) in the amorphous state were miscible in all of the blend compositions studied, as evidenced by a single, composition‐dependent glass‐transition temperature observed for each blend composition. The variation in the glass‐transition temperature with the blend composition was well predicted by the Gordon–Taylor equation, with the fitting parameter being 0.91. The cold‐crystallization (peak) temperature decreased with an increasing PTT content, whereas the melt‐crystallization (peak) temperature decreased with an increasing amount of the minor component. The subsequent melting behavior after both cold and melt crystallizations exhibited melting point depression behavior in which the observed melting temperatures decreased with an increasing amount of the minor component of the blends. During crystallization, the pure components crystallized simultaneously just to form their own crystals. The blend having 50 wt % of PTT showed the lowest apparent degree of crystallinity and the lowest tensile‐strength values. The steady shear viscosity values for the pure components and the blends decreased slightly with an increasing shear rate (within the shear rate range of 0.25–25 s^?1); those of the blends were lower than those of the pure components. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 676–686, 2004     

聚乙烯亚胺复合铜微粒的制备及表征

以溶液还原法对聚乙烯亚胺（PEI）和Cu2＋形成的配合物进行还原,制备了金属Cu微粒。扫描电镜对微粒的分析表明,低浓度Cu2＋配合物制备的微粒形态规则、分布均匀,粒径约0.98μm。红外光谱、X-衍射对微粒组成的分析表明,PEI键合地包覆Cu微粒,没有Cu的其他氧化物存在,PEI包覆量占微粒质量的14.6%,形成的复合...     

Structural Study on Water-induced Phase Transitions of Poly(ethylene imine) as Viewed from the Simultaneous Measurements of Wide-Angle X-ray Diffractions and DSC Thermograms

Thermal behavior of poly(ethylene imine) [PEI] has been studied using simultaneous WAXD/DSC measurement system. PEI exhibits water-induced and thermally-induced phase transitions among four kinds of crystalline hydrates: anhydrate (EI/water = 1/0), hemihydrate (1/0.5), sesquihydrate (1/1.5), and dihydrate (1/2). The chain conformation changes from a double helix in the anhydrate to a planar zigzag form in the three hydrates. The anhydrate melts at 60 °C while the hydrates melt differently in the temperature region of 70–110 °C. By means of the simultaneous WAXD/DSC measurements, complex DSC thermograms of PEI hydrates were characterized on the basis of X-ray diffractions obtained concurrently.     

Kinetic Investigations on the Polymerization of 2‐Oxazolines Using Pluritriflate Initators

In our ongoing efforts to develop poly(2‐oxazoline)s (POx) for biomedical applications, we report on the preparation of defined, star‐like hydrophilic POx. Using pluritriflate initiators, we show, through online kinetic measurements by gas chromatography, that multiple initiating groups are of equal reactivity for the initiation of the polymerization of 2‐oxazolines. The overall polymerization rate increases linearly with the number of initiator functions per molecule. Thus, all initiating moieties are of the same reactivity and all arms grow at the same rate. This is crucial for the establishment of a meaningful structure‐property relationship for polymers of star architectures.

     

Fiber property and structure development of polyester blend fibers reinforced with a thermotropic liquid‐crystal polymer

Ternary blend fibers (TBFs), based on melt blends of poly(ethylene 2,6‐naphthalate), poly(ethylene terephthalate), and a thermotropic liquid‐crystal polymer (TLCP), were prepared by a process of melt blending and spinning to achieve high‐performance fibers. The reinforcement effect of the polymer matrix by the TLCP component, the fibrillar structure with TLCP fibrils of high aspect ratios, and the development of more ordered and perfect crystalline structures by an annealing process resulted in the improvement of the tensile strength and modulus for the TBFs. An increase in the apparent crystallite size with the spinning speed was attributed to the development of larger crystallites and more ordered crystalline structures in the annealed TBFs. The birefringence and density of the TBFs increased with increasing spinning speed, the TBFs becoming more oriented and the crystal packing becoming more enhanced. The molecular orientation was an important factor in determining the tensile strength and modulus of the TBFs. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 395–403, 2004     

Development,Characterization, and Antimicrobial Evaluation of Ampicillin-Loaded Nanoparticles Based on Poly(maleic acid-co-vinylpyrrolidone) on Resistant Staphylococcus aureus Strains

This study was focused on synthesizing, characterizing, and evaluating the antimicrobial effect of polymer nanoparticles (NPs) loaded with ampicillin. For this, the NPs were produced through polymeric self-assembly in aqueous media assisted by high-intensity sonication, using anionic polymers corresponding to the sodium salts of poly(maleic acid-co-vinylpyrrolidone) and poly(maleic acid-co-vinylpyrrolidone) modified with decyl-amine, here named as PMA-VP and PMA-VP-N10, respectively. The polymeric NPs were analyzed and characterized through the formation of polymeric pseudo-phases utilizing pyrene as fluorescent probe, as well as by measurements of particle size, zeta potential, polydispersity index, and encapsulation efficiency. The antimicrobial effect was evaluated by means of the broth microdilution method employing ampicillin sensitive and resistant Staphylococcus aureus strains. The results showed that PMA-VP and PMA-VP-N10 polymers can self-assemble, forming several types of hydrophobic pseudo-phases with respect to the medium pH and polymer concentration. Likewise, the results described that zeta potential, particle size, polydispersity index, and encapsulation efficiency are extremely dependent on the medium pH, whereas the antimicrobial activity displayed an interesting recovery of antibiotic activity when ampicillin is loaded in the polymeric NPs.