Chitosan‐modified d‐α‐tocopheryl poly(ethylene glycol) 1000 succinate‐b‐poly(ε‐caprolactone‐ran‐glycolide) nanoparticles for the oral chemotherapy of bladder cancer

Oral chemotherapy is quickly emerging as an appealing option for cancer patients. It is less stressful because the patient has fewer hospital visits and can still maintain a close relationship with health care professionals. Three kinds of nanoparticles made from commercial poly(ε‐caprolactone) (PCL) and self‐synthesized d‐α‐tocopheryl poly(ethylene glycol) 1000 succinate ‐b‐poly(ε‐caprolactone‐ran‐glycolide) [TPGS‐b‐(PCL‐ran‐PGA)] diblock copolymer were prepared in this study for the oral delivery of antitumor agents, including chitosan‐modified PCL nanoparticles, nonmodified TPGS‐b‐(PCL‐ran‐PGA) nanoparticles, and chitosan‐modified TPGS‐b‐(PCL‐ran‐PGA) nanoparticles. First, the TPGS‐b‐(PCL‐ran‐PGA) diblock copolymer was synthesized and structurally characterized. Chitosan was adopted to extend the retention time at the cell surface and thus increase the chance of nanoparticle uptake by the gastrointestinal mucosa and improve the absorption of drugs after oral administration. The resulting TPGS‐b‐(PCL‐ran‐PGA) nanoparticles were found to be of spherical shape and around 200 nm in diameter with a narrow size distribution. The surface charge of the TPGS‐b‐(PCL‐ran‐PGA) nanoparticles could be reversed from anionic to cationic after surface modification. The chitosan‐modified TPGS‐b‐(PCL‐ran‐PGA) nanoparticles displayed a significantly higher level of cellular uptake compared with the chitosan‐modified PCL nanoparticles and nonmodified TPGS‐b‐(PCL‐ran‐PGA) nanoparticles. In vitro cell viability studies showed the advantages of the chitosan‐modified TPGS‐b‐(PCL‐ran‐PGA) nanoparticles over Taxol in terms of their cytotoxicity against human RT112 cells. In summary, the oral delivery of antitumor agents by chitosan‐modified TPGS‐b‐(PCL‐ran‐PGA) nanoparticles produced results that were promising for the treatment of patients with bladder cancer. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2118–2126, 2013     

Bio‐Based Hybrid Magnetic Latex Particles Containing Encapsulated γ ‐Fe2O3 by Miniemulsion Copolymerization of Soybean Oil‐Acrylated Methyl Ester and Styrene

This work reports the use of acrylated fatty acid methyl ester (AFAME) as a biomonomer for the synthesis of bio‐based hybrid magnetic particles poly(styrene‐co‐AFAME)/γ‐Fe₂O₃ produced by miniemulsion polymerization. Poly(styrene‐co‐AFAME)/γ‐Fe₂O₃ can be tailored for use in various fields by varying the content of AFAME. The strategy employed is to encapsulate superparamagnetic iron oxide nanoparticles (SPIONs) as γ‐Fe₂O₃ into a styrene/AFAME‐based copolymer matrix. Raman spectroscopy is employed to ensure the formation of the SPIONs (γ‐Fe₂O₃) obtained by a co‐precipitation technique followed by oxidation of Fe₃O₄. The functionalization of SPIONs with oleic acid (OA) is carried out to increase the SPIONs–monomer affinity. The presence of OA on the surface of γ‐Fe₂O₃ is certified by identification of main absorption bands by fourier‐transform infrared spectroscopy (FTIR). Thermal analysis (differential thermogravimetry/differential thermo analysis and differential scanning calorimetry) results of poly(styrene‐co‐AFAME)/γ‐Fe₂O₃ show an increase in AFAME content leading to a lower copolymer glass transition temperature (T _g). Dynamic light scattering (DLS) measurements result in poly(styrene‐co‐AFAME)/γ‐Fe₂O₃ particles with diameter in the range of 100–150 nm. It is also observed by transmission electron microscopy (TEM) and cryo‐TEM techniques that γ‐Fe₂O₃ particles are successfully encapsulated into the poly(styrene‐co‐AFAME) matrix.     

Morphology and thermomechanical properties of epoxy thermosets modified with polysulfone‐block‐polydimethylsiloxane multiblock copolymer

Polysulfone‐block‐polydimethylsiloxane (PSF‐b‐PDMS) multiblock copolymer was synthesized via the Mannich polycondensation between phenolic hydroxyl‐terminated polysulfone and aminopropyl‐terminated polydimethylsiloxane in the presence of formaldehyde. The multiblock copolymer was characterized by means of nuclear magnetic resonance spectroscopy (NMR) and gel permeation chromatography (GPC) and used as a modifier to improve the thermomechanical properties of epoxy thermosets. Transmission electron microscopy (TEM) showed that the epoxy thermosets containing PSF‐b‐PDMS multiblock copolymer possesses the microphase‐separated morphological structures. Depending on the content of the PSF‐b‐PDMS multiblock copolymer, the spherical particles with the size of 50–200 nm in diameter were dispersed into the continuous epoxy matrices. The measurement of static contact angles showed that with the inclusion of PSF‐b‐PDMS multiblock copolymer, the epoxy thermosets displayed the improved surface hydrophobicity. It is noted that the epoxy resin was significantly toughened in terms of the measurement of critical stress field intensity factor (K_1C). © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Efficient removal of Cu(II) using amino‐functionalized superparamagnetic nanoparticles prepared via SI‐ATRP

An amino‐functionalized nano‐adsorbent (DETA‐MNPs) was prepared by a process involving: (1) synthesis of superparamagnetic Fe₃O₄ nanoparticles; (2) introduction of amino groups after which ATRP initiator was anchored; (3) grafting of glycidyl methacrylate (GMA) via SI‐ATRP; and (4) ring‐opening reaction of epoxy groups with diethylenetriamine (DETA). The nano‐adsorbent was characterized by Fourier transform infrared spectroscopy (FT‐IR), X‐ray diffraction (XRD), transmission electron microscope (TEM), and vibrating sample magnetometer (VSM) and applied to remove Cu(II) in batch experiments. The effects of pH, Cu(II) concentrations, solution ionic strength, and contact time were investigated. The results show that the DETA‐MNPs are spherical with cubic spine structure, high saturation magnetization (41.9 emu g^?1), and an average diameter of 10 nm. The maximum Cu(II) adsorption capacity achieves 83.33 mg g^?1 at pH 5.0 by Langmuir model. The adsorption process is highly pH‐dependent and reaches equilibrium within 20 min. Furthermore, the DETA‐MNPs exhibit excellent dispersibility and reusability. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 132, 42859.     

Synthesis and characterization of energetic GAP‐b‐PAEMA block copolymer

Energetic block copolymer of polyglycidylazide‐b‐poly (azidoethyl methacrylate) (GAP‐b‐PAEMA) was synthesized and characterized. Macroinitiator PECH‐Br prepared via the reaction of 2‐bromoisobutyryl bromide with hydroxyl‐terminated polyepichlorohydrin (PECH‐OH) was used to initiate the atom transfer radical polymerization (ATRP) of chloroethyl methacrylate (CEMA). After azidation of the resulting copolymer, energetic copolymer GAP‐b‐PAEMA was obtained. Increase in the molecular weight determined by gel permeation chromatograph (GPC) is in agreement with the formation of block copolymer. Fourier transform infrared spectroscopy (FTIR) shows that the chlorine groups in the block copolymer can be substituted by azide group easily. Thermogravimetric analysis (TGA) shows that degradation of GAP‐b‐PAEMA involves two steps: the instantaneous decomposition of the azide groups followed by progressive scission of the polymer backbone. From differential scanning calorimetry (DSC) analysis, the GAP‐b‐PAEMA copolymer exhibits two glass transition temperatures (T_g) at ?18 and 36°C, suggesting that the synthesized copolymer is a thermoplastic elastomer. This research provides a new method for the synthesis of energetic polymer. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

PEGylated polylysine derived copolymers with reduction‐responsive side chains for anticancer drug delivery

Reduction‐responsive drug delivery systems have recently gained intense attention in intracellular delivery of anticancer drugs. In this study, we developed a PEGylated polypeptide, poly(ethylene glycol)‐block‐poly(?‐propargyloxycarbonyl‐l ‐lysine) (PEG₁₁₃‐b‐PPAL), as a novel clickable substrate for conjugation of reduction‐responsive side chains for antineoplastic drug delivery. PEG₁₁₃‐b‐PPAL was synthesized through ring‐opening polymerization of alkyne‐containing N‐carboxyanhydride monomers. A designed disulfide‐containing side chain was introduced onto the PEGylated polypeptide by click reaction. The obtained copolymer PEG₁₁₃‐b‐P(Lys‐DSA) formed micelles by self‐assembly, which exhibited reduction‐responsive behavior under the stimulus of 10 mmol L^–1 glutathione (GSH) in water. A small molecule intermediate, compound 2 , was used as a model to investigate the thiol reduction mechanism of PEG₁₁₃‐b‐P(Lys‐DSA) copolymers. The anticancer drug doxorubicin (DOX) was then loaded into the micelles with a drug loading content of 6.73 wt% and a loading efficiency of 40.3%. Both the blank and the drug‐loaded micelles (DOX‐loaded polylysine derived polymeric micelles (LMs/DOX)) adopted a spherical morphology, with average diameters of 48.0 ± 13.1 and 63.8 ± 20.0 nm, respectively. The in vitro drug release results indicated that DOX could be released faster from the micelles by the trigger of GSH in phosphate buffered saline. Confocal laser scanning microscopy and flow cytometer analysis further proved the intracellular delivery of DOX by LMs/DOX and their GSH‐sensitive release behavior. A 3‐(4,5‐dimethyl‐thiazol‐2‐yl)‐2,5‐diphenyl tetrazolium bromide assay showed that the polymers exhibited negligible cytotoxicity towards normal L929 cells or cancer MCF‐7 cells with a treated concentration up to 1.0 mg mL^–1. In conclusion, our synthesized biocompatible and biodegradable PEGylated polypeptides hold great promise for intracellular antineoplastic drug delivery. © 2019 Society of Chemical Industry     

Gadolinium‐conjugated FA‐PEG‐PAMAM‐COOH nanoparticles as potential tumor‐targeted circulation‐prolonged macromolecular MRI contrast agents

The aim of research is to develop potential tumor‐targeted circulation‐prolonged macromolecular magnetic resonance imaging (MRI) contrast agents without the use of low molecular gadolinium (Gd) ligands. The contrast agents were based on polymer–metal complex nanoparticles with controllable particle size to achieve the active and passive tumor‐targeted potential. In particular, poly (amidoamine) (PAMAM) dendrimer with 32 carboxylic groups was modified with folate‐conjugated poly (ethyleneglycol) amine (FA‐PEG‐NH₂, M_w: 2 k and 4 kDa). FA‐PEG‐PAMAM‐Gd macromolecular MRI contrast agents were prepared by the complex reaction between the carboxylic groups in PAMAM and GdCl₃. The structure of FA‐PEG‐PAMAM‐COOH was confirmed by nuclear magnetic resonance (¹H‐NMR), Fourier transform infrared (FTIR) spectra, and electrospray ionization mass spectra (ESI‐MS). The mass percentage content of Gd (III) in FA‐PEG‐PAMAM‐Gd was measured by inductively coupled plasma‐atomic emission spectrometer (ICP‐AES). The sizes of these nanoparticles were about 70 nm measured by transmission electron microscopy, suggestion of their passive targeting potential to tumor tissue. In comparison with clinically available small molecular Gadopentetate dimeglumine, FA‐PEG‐PAMAM‐Gd showed comparable cytotoxicity and higher relaxation rate, suggestion of their great potential as tumor‐targeted nanosized macromolecular MRI contrast agents due to the overexpressed FA receptor in human tumor cell surfaces. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Chemo‐enzymatic synthesis of poly(2,2,2‐trichloroethyl 10‐hydroxydecanate)‐block‐polystyrene combining enzymatic self‐condensation polymerization and ATRP

Enzymatic polymerization in a non‐natural environment is of interest as an environmentally friendly methodology as an alternative to the use of conventional chemical organometallic catalysts. Chemo‐enzymatic synthesis of the AB‐type diblock copolymer poly(2,2,2‐trichloroethyl 10‐hydroxydecanate)‐block‐polystyrene (PHD‐b‐PSt) was carried out by combining enzymatic self‐condensation polymerization (eSCP) and atom‐transfer radical polymerization (ATRP). Biocatalyst Novozyme 435 was successful in catalyzing the eSCP of a novel ω‐hydroxyester, i.e. 2,2,2‐trichloroethyl 10‐hydroxydecanate. The resulting ? CCl₃‐terminated PHD initiated the ATRP of styrene, a ‘living’/controlled radical polymerization. The analysis of the hydrolysate from the copolymer proved the presence of a block copolymer structure. In addition, the well‐defined diblock copolymer PHD‐b‐PSt self‐assembled into nanoscale micelles in aqueous solution. The chemo‐enzymatic synthesis of diblock copolymer PHD‐b‐PSt was achieved by the combination of eSCP and ATRP. The structures and composition of the block copolymer were characterized by means of NMR, infrared and gel permeation chromatography measurements. Differential scanning calorimetry analysis showed that a microphase‐separation structure was formed in the copolymer, which was caused by the crystallization of the PHD segments. As investigated with atomic force microscopy and dynamic light scattering, these micelles had a mean diameter and a spherical shape. To our knowledge, this is the first example of a chemo‐enzymatic synthesis based on eSCP and ATRP. Copyright © 2007 Society of Chemical Industry     

Crystallization behavior of “wet brush” and “dry brush” blends of PS‐b‐PEO‐b‐PS/h‐PEO

The crystallization behavior of the blending system consists of homopolymer poly(ethylene oxide) (h‐PEO) with different molecular weights, and polystyrene‐block‐poly (ethylene oxide)‐block‐polystyrene (PS‐b‐PEO‐b‐PS) triblock copolymer has been investigated by DSC measurements. The crystallization of PEO block (b‐PEO) in block copolymer occurs under much lower temperature than that of the h‐PEO in the bulk (ΔT > 65 °C), which is attributed to the homogeneous nucleation crystallization behavior of the b‐PEO microdomains. In both the “dry‐brush” and the “wet brush” blending systems, the homogeneous nucleation crystallization temperature of PS‐b‐PEO‐b‐PS/h‐PEO blends increases due to the increase of the domain size. The heterogeneous nucleation crystallization temperatures of h‐PEO in the wet brush blending systems are higher than that of the corresponding h‐PEO in the bulk. At the same time, the heterogeneous nucleation crystallization temperature of b‐PEO10000 decreases from 43°C to 30°C and 40°C in the h‐PEO600 and h‐PEO2000 blending systems, respectively, because of the stretching of the PEO chains in the wet brush. However, this kind of phenomenon does not happen in the dry brush blending systems. The self‐seeding procedure was used to further ascertain the nucleation mechanism in the crystallization process. As a result, the self‐seeding domains have been confirmed, and the difference between the dry brush and wet brush systems has been observed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Preparation and characterization of magnetic star‐shaped amphiphilic copolymer nanoparticles of S‐Fe3O4‐PLA‐b‐MPEG

Magnetic star‐shaped amphiphilic copolymers (S‐Fe₃O₄‐PLA‐b‐MPEG) consisting of Fe₃O₄ as the core, poly(L ,D ‐lactide) (PLA) as the inner layer, and monomethyl polyethylene glycol (MPEG) as the out shell were synthesized. The syntheses included ring‐opening polymerization of L ,D ‐lactide initiated by hydroxyl modified Fe₃O₄ (Fe₃O₄‐(OH) _n), followed by the esterification of the PLA with MPEG. The structure of the star block copolymers were characterized by Fourier Transform infrared spectroscopy, thermogravimetric analysis, X‐ray diffraction, transmission electron microscopy, nanoparticle size analyzer, and vibrating sample magnetometer. The nanoparticles in aqueous solution were made from the amphiphilic star copolymer. The average size of the nanoparticles was adjustable and increased with the increase of the PLA segments in the copolymer. The cytotoxicity grade of the nanoparticles was zero determined by the analysis of cytotoxicity. The nanoparticles could potentially be used as the drug vehicles for magnetic‐response controlled release. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Influences of the chain structure of PE‐b‐PEG on the properties of PE/PE‐b‐PEG blend membranes prepared by TIPS

In this article, a series of diblock copolymer polyethylene‐b‐ poly(ethylene glycol)s (PE‐b‐PEGs) with various molecular weight of polyethylene segment was blended with linear low‐density PE. The PE/PE‐b‐PEG blend porous membranes with high porosity were obtained by thermally induced phase separation (TIPS) process. The isothermal crystallization kinetics of PE/LP/PE‐b‐PEG blends indicated that the introduction of PE‐b‐PEG could inhibit the growth rate of polyethylene crystals which could increase the pore size and porosity of the membranes. The PE/PE‐b‐PEG blend membranes with PE₁₃₀₀‐b‐PEG₂₂₀₀ showed the largest pore size and porosity due to its crystallization behavior during TIPS. The surface of the membranes became smoother and the morphology of the membranes could be effectively tuned by introducing PE‐b‐PEG. Compared with the PE membrane, the PE/PE‐b‐PEG blend membranes exhibited higher hydrophilicity (the water contact angle decreased from 112° to 84°), water permeability (the permeation flux increased from 80 to 440 L/m² h under 0.1 MPa), rejection performance (completely reject carbon particles in the filtration of carbon ink solution), and fouling resistance (the value of protein adsorption dropped from 0.25 to 0.05 mg/cm²). The hydrophilicity and fouling resistance of PE/PE‐b‐PEG blend membranes increased as the length of PE segment in PE‐b‐PEGs decreased. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46499.     

Dual‐stimuli‐responsive polymer‐coated mesoporous silica nanoparticles used for controlled drug delivery

In this article, a temperature‐ and pH‐responsive delivery system based on block‐copolymer‐capped mesoporous silica nanoparticles (MSNs) is presented. A poly[2‐(diethylamino)ethyl methacrylate)] (PDEAEMA)‐b‐poly(N‐isopropyl acrylamide) (PNIPAM) shell on MSNs was obtained through the surface‐initiated atom transfer radical polymerization. The block copolymer PDEAEMA‐b‐PNIPAM showed both temperature‐ and pH‐responsive properties. The release of the loaded model molecules from PDEAEMA‐b‐PNIPAM‐coated MSNs could be controlled by changes in the temperature or pH value of the medium. The as‐desired drug‐delivery carrier may be applied to biological systems in the future. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42395.     

Synthesis of amphiphilic triblock copolymers for the formation of magnesium fluoride (MgF2) nanoparticles

A series of amphiphilic poly(2‐hydroxyethyl methacrylate)‐b‐polydimethylsiloxane‐b‐poly(2‐hydroxyethyl methacrylate) (pHEMA‐b‐PDMS‐b‐pHEMA) (A‐B‐A) triblock copolymers were synthesized from three different carbinol‐terminated polydimethylsiloxanes with varying molecular weight. A carbinol‐terminated polydimethylsiloxane was modified with 2‐bromoisobutyryl bromide to obtain a macroinitiator. The block copolymers were characterized by NMR, GPC, and dynamic light scattering (DLS). Reverse micelles of a copolymer were formed in mixture of benzene/methanol solution which served as nanoreactors for the synthesis of magnesium fluoride (MgF₂) nanoparticles. The MgF₂ was prepared via chemical precipitation using magnesium chloride and potassium fluoride as reactants. The MgF₂‐triblock copolymer composites were synthesized as a function of MgF₂–weight ratio (0.5, 5, and 10 wt%) in copolymer. The MgF₂ colloids were dissolved in three organic solvents: methanol, isopropanol, and tetrahydrofuran. The polymer nanoparticles were characterized by DLS, transmission electron microscopy, thermogravimetric analysis, and X‐ray diffraction (XRD) analysis. The formation of MgF₂ crystals was observed by XRD. Particle size and particle size distribution showed significant changes in different solvents. The thermal stability of MgF₂ colloids increased as the amount of nanoparticle increased in polymeric matrix. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis and characterization of biodegradable block copolymer pluronic‐b‐poly(L‐lysine)

This study presented the investigations on the synthesis of a novel biodegradable block copolymer of pluronic‐b‐poly(L ‐lysine) (pluronic‐b‐PLL), which combined the characteristics of aliphatic polyester and poly(amino acids). The synthesis work started with end‐capping of pluronic with N‐t‐butoxycarbonyl‐L ‐phenylalanine using dicyclohexylcarbodiimide in the presence of 4‐dimethylaminopyridine, followed by a deprotection process to obtain the amino‐terminated pluronic; the new primary amino group in the modified pluronic initiated ring‐opening polymerization of amino acid N‐carboxyanhydride, which afforded the pluronic‐b‐poly(N^ε‐(Z)‐L ‐lysine) block copolymer. Finally, removal of the side‐chain N^ε‐(carbonybenzoxy) end protecting groups yields the block copolymer of pluronic‐b‐PLL. The products were characterized by ¹H‐NMR, FTIR, DSC, and GPC. The block copolymer micelle containing the anticancer drug paclitaxel was prepared by the double emulsion method. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

A novel method for preparing silver/poly(siloxane‐b‐methyl methacrylate) nanocomposites with multiple properties in the DMF‐toluene mixture solvent

A novel method for preparing silver/poly(siloxane‐b‐methyl methacrylate) (Ag/(PDMS‐b‐PMMA)) hybrid nanocomposites was proposed by using the siloxane‐containing block copolymers as stabilizer. The reduction of silver nitrate (AgNO₃) was performed in the mixture solvent of dimethyl formamide (DMF) and toluene, which was used to dissolve double‐hydrophobic copolymer, as well as served as the powerful reductant. The presence of the PMMA block in the copolymer indeed exerted as capping ligands for nanoparticles. The resultant nanocomposites exhibited super hydrophobicity with water contact angle of 123.3^° and the thermogravimetry analysis (TGA) revealed that the resultant nanocomposites with more PDMS were more heat‐resisting. Besides, the antimicrobial efficiency of the most desirable nanocomposite (Ag/PDMS₆₅‐b‐PMMA₃₀ loaded with 7.3% silver nanoparticle) could reach up to 99.4% when contacting with escherichia coli within 120 min. As a whole, the resultant nanocomposites by the integration of excellent properties of silver nanoparticles as well as siloxane‐block copolymers can be a promising for the development of materials with hydrophobic, heat‐resisting and outstanding antibacterial properties from the chemical product engineering viewpoint. © 2013 American Institute of Chemical Engineers AIChE J, 59: 4780–4793, 2013     

The Interplay between Fe3O4 Superparamagnetic Nanoparticles,Sodium Butyrate,and Folic Acid for Intracellular Transport

Combined treatments which use nanoparticles and drugs could be a synergistic strategy for the treatment of a variety of cancers to overcome drug resistance, low efficacy, and high-dose-induced systemic toxicity. In this study, the effects on human colon adenocarcinoma cells of surface modified Fe₃O₄ magnetic nanoparticles (MNPs) in combination with sodium butyrate (NaBu), added as a free formulation, were examined demonstrating that the co-delivery produced a cytotoxic effect on malignant cells. Two different MNP coatings were investigated: a simple polyethylene glycol (PEG) layer and a mixed folic acid (FA) and PEG layer. Our results demonstrated that MNPs with FA (FA-PEG@MNPs) have a better cellular uptake than the ones without FA (PEG@MNPs), probably due to the presence of folate that acts as an activator of folate receptors (FRs) expression. However, in the presence of NaBu, the difference between the two types of MNPs was reduced. These similar behaviors for both MNPs likely occurred because of the differentiation induced by butyrate that increases the uptake of ferromagnetic nanoparticles. Moreover, we observed a strong decrease of cell viability in a NaBu dose-dependent manner. Taking into account these results, the cooperation of multifunctional MNPs with NaBu, taking into consideration the particular cancer-cell properties, can be a valuable tool for future cancer treatment.     

Thermal and mechanical properties of nanocomposites based on a PLLA‐b‐PEO‐b‐PLLA triblock copolymer and nanohydroxyapatite

Composites which combine biocompatible polymers and hydroxyapatite are unique materials with regards to their mechanical properties and bioactivity in the development of temporary bone‐fixation devices. Nanocomposites based on a biocompatible and amphiphilic triblock copolymer of poly(l‐ lactide) (PLLA) and poly(ethylene oxide) (PEO) —PLLA‐b‐PEO‐b‐PLLA— and neat (nHAp) or PEO‐modified (nHAp@PEO) hydroxyapatite nanoparticles were prepared by dispersion in benzene solutions, followed by freeze‐drying and injection moulding processes. The morphology of the copolymers of a PEO block dispersed throughout a PLLA matrix was not changed with addition of the nanofillers. The nHAp particles were spherical and, after modification, the nHAp@PEO nanoparticles were partially agglomerated. In the nanocomposites, these particles characteristics remained unchanged, and the nHAp particles and nHAp@PEO agglomerates were uniformly dispersed through the copolymer matrix. These particles acted as nucleating agents, with nHAp@PEO being more efficient. The incorporation of nHAp increased both the reduced elastic modulus (～22%) and the indentation hardness (～15%) in comparison to the copolymer matrix, as determined by nanoindentation tests, while nHAp@PEO addition resulted in lower increments of these mechanical parameters. The incorporation of untreated nHAp was, therefore, more beneficial with regards to the mechanical properties, since the amphiphilic PLLA‐b‐PEO‐b‐PLLA matrix was already efficient for nHAp nanoparticles dispersion. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44187.     

Thermosensitive polymeric micelles based on the triblock copolymer poly(d,l‐lactide)‐b‐poly(N‐isopropyl acrylamide)‐b‐poly(d,l‐lactide) for controllable drug delivery

A thermosensitive amphiphilic triblock copolymer, poly(d,l ‐lactide) (PLA)‐b‐poly(N‐isopropyl acrylamide) (PNIPAAM)‐b‐PLA, was synthesized by the ring‐opening polymerization of d,l ‐lactide; the reaction was initiated from a dihydroxy‐terminated poly(N‐isopropyl acrylamide) homopolymer (HO‐PNIPAAM‐OH) created by radical polymerization. The molecular structure, thermosensitive characteristics, and micellization behavior of the obtained triblock copolymer were characterized with Fourier transform infrared spectroscopy, ¹H‐NMR, gel permeation chromatography, dynamic light scattering, and transmission electron microscopy. The obtained results indicate that the composition of PLA‐b‐PNIPAAM‐b‐PLA was in good agreement with what was preconceived. This copolymer could self‐assemble into spherical core–shell micelles (ca. 75–80 nm) in aqueous solution and exhibited a phase‐transition temperature around 26 °C. Furthermore, the drug‐delivery properties of the PLA‐b‐PNIPAAM‐b‐PLA micelles were investigated. The drug‐release test indicated that the synthesized PLA‐b‐PNIPAAM‐b‐PLA micelles could be used as nanocarriers of the anticancer drug adriamycin (ADR) to effectively control the release of the drug. The drug‐delivery properties of PLA‐b‐PNIPAAM‐b‐PLA showed obvious thermosensitive characteristics, and the release time of ADR could be extended to 50 h. This represents a significant improvement from previous PNIPAAM‐based drug‐delivery systems. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45304.     

Relationship between the crystallization behavior of poly(ethylene glycol) and stereocomplex crystallization of poly(L‐lactic acid)/poly(D‐lactic acid)

Poly(l ‐lactic acid) (PLLA) is a good biomedical polymer material with wide applications. The addition of poly(ethylene glycol) (PEG) as a plasticizer and the formation of stereocomplex crystals (SCs) have been proved to be effective methods for improving the crystallization of PLLA, which will promote its heat resistance. In this work, the crystallization behavior of PEG and PLLA/poly(d ‐lactic acid) (PDLA) in PLLA/PDLA/PEG and PEG‐b‐PLLA/PEG‐b‐PDLA blends has been investigated using differential scanning calorimetry, polarized optical microscopy and X‐ray diffraction. Both SCs and homocrystals (HCs) were observed in blends with asymmetric mass ratio of PLLA/PDLA, while exclusively SCs were observed in blends with approximately equal mass ratio of PLLA/PDLA. The crystallization of PEG was only observed for the symmetric blends of PLLA_39k/PDLA_35k/PEG_2k, PLLA_39k/PDLA_35k/PEG_5k, PLLA_69k/PDLA_96k/PEG_5k and PEG‐b‐PLLA_31k/PEG‐b‐PDLA_27k, where the mass ratio of PLLA/PDLA was approximately 1/1. The results demonstrated that the formation of exclusively SCs would facilitate the crystallization of PEG, while the existence of both HCs and SCs could restrict the crystallization of PEG. The crystallization of PEG is related to the crystallinity of PLLA and PDLA, which will be promoted by the formation of SCs. © 2017 Society of Chemical Industry     

Silica/polystyrene and silica/polystyrene‐b‐polymethacryloxypropyltrimethoxysilane hybrid nanoparticles via surface‐initiated ATRP and comparison of their wettabilities

Both silica/polystyrene (SiO₂/PS) and silica/polystyrene‐b‐polymethacryloxypropyltrimethoxysilane (SiO₂/PS‐b‐PMPTS) hybrid nanoparticles were synthesized via surface‐initiated atom transfer radical polymerization (SI‐ATRP) from SiO₂ nanoparticles. The growths of all polymers via ATRP from the SiO₂ surfaces were well controlled as demonstrated by the macromolecular characteristics of the grafted chains. Their wettabilities were measured and compared by water contact angle (WCA) and surface roughness. The results show that the nanoparticles possess hydrophobic surface properties. The static WCA of SiO₂/PS‐b‐PMPTS hybrid nanoparticles is smaller than that of SiO₂/PS hybrid nanoparticles, meanwhile, the surface roughness of SiO₂/PS‐b‐PMPTS hybrid nanoparticles is yet slightly rougher than that of SiO₂/PS hybrid nanoparticles, which shows that the combination and competition of surface chemistry and roughness of a solid material can finally determine its wettability. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers