Thermally and magnetically dual‐responsive mesoporous silica nanospheres: preparation,characterization, and properties for the controlled release of sophoridine

Novel thermally and magnetically dual‐responsive mesoporous silica nanoparticles [magnetic mesoporous silica nanospheres (M‐MSNs)–poly(N‐isopropyl acrylamide) (PNIPAAm)] were developed with magnetic iron oxide (Fe₃O₄) nanoparticles as the core, mesoporous silica nanoparticles as the sandwiched layer, and thermally responsive polymers (PNIPAAm) as the outer shell. M‐MSN–PNIPAAm was initially used to control the release of sophoridine. The characteristics of M‐MSN–PNIPAAm were investigated by transmission electron microscopy, Fourier transform infrared spectroscopy, X‐ray diffraction, thermogravimetry, N₂ adsorption–desorption isotherms, and vibrating specimen magnetometry analyses. The results indicate that the Fe₃O₄ nanoparticles were incorporated into the M‐MSNs, and PNIPAAm was grafted onto the surface of the M‐MSNs via precipitation polymerization. The obtained M‐MSN–PNIPAAm possessed superparamagnetic characteristics with a high surface area (292.44 m²/g), large pore volume (0.246 mL/g), and large mesoporous pore size (2.18 nm). Sophoridine was used as a drug model to investigate the loading and release properties at different temperatures. The results demonstrate that the PNIPAAm layers on the surface of M‐MSN–PNIPAAm effectively regulated the uptake and release of sophoridine. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40477.     

Electrically modulated transport of diclofenac salts through hydrogels of sodium alginate,carbopol, and their blend polymers

The electrically modulated transdermal migration of diclofenac sodium (DS), diclofenac potassium (DP), and diclofenac diethylammonium (DD) drugs from the hydrogels of sodium alginate (NaAlg), carbopol (CP), and blends of NaAlg with CP prepared in 2:1, 2:1.5, and 2:2 ratios was investigated. The release of DS, DP, and DD was investigated through excised rat skin to study the effects of viscosity, pH, and the ionic strength of the receptor medium under the influence of an electrical current in a switch‐on and switch‐off mode. A pulsatile pattern of transport was observed that depended on the presence or absence of an electrical current. Drug transport was dependent on the electrical current, the ionic nature of drugs, and the ionic strength of the diffusion medium. Drug transport followed the sequence DS > DP > DD. A decrease in viscosity and an increase in the pH of the hydrogel were observed when an electrical current was applied. CP was more responsive to an electrical stimulus, but the rate of transport was higher for NaAlg. Increasing the amount of CP in the blends increased the electrical responsiveness. The blend hydrogel with a high CP content showed the highest enhancement in drug transport, whereas the NaAlg hydrogel showed the least. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 301–311, 2005     

Drug transport in stimuli responsive acrylic and methacrylic interpenetrating polymer networks

The interpenetrating polymer networks (IPNs) are recently gaining attention as sustained drug delivery systems because they could ensure a proper combination of functionality and network density to control the drug release profiles. This study aims to reveal how the functionality of two IPNs based on polyacrylamide and respectively poly(acrylic acid) (PAA) and poly(methacrylic acid) (PMAA) influences their smart behavior as well as their properties as delivery systems of the cationic drug verapamil hydrochloride (VPM). The “extra” α‐methyl group of PMAA results into a loss of the temperature sensitivity in the studied region and changes the pH responsivity of the PMAA/PAAM IPNs as compared to the PAA/PAAM IPNs. Moreover, the VPM diffusion in both IPNs depends on their composition due to the change in their functionality as well as of their network density. The “extra” α‐methyl group of PMAA defines its enhanced hydrophobicity and hence influences the VPM diffusion mechanism. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45380.     

Sustained release behavior of pH‐responsive poly(vinyl alcohol)/poly(acrylic acid) hydrogels containing activated carbon fibers

The composites of pH‐responsive poly(vinyl alcohol)/poly(acrylic acid) hydrogel and activated carbon fibers (ACFs) were prepared as sustained drug release system with excellent mechanical properties. The mechanical properties of hydrogels were improved greatly by addition of ACFs. The thinner ACFs were more effective in increasing the mechanical properties of composite hydrogels. The cumulative amount of release and the release period were dependent on the surface area and the pore volume of ACFs. The drug release was maximized at basic condition due to the pH‐sensitive hydrogel matrices and the initial bust phenomenon was alleviated by incorporating ACFs in the hydrogels. The drug release was sustained about four times longer and the mechanical property was increased about 2.6 times higher because ACFs worked as drug reservoir and reinforcement. Cytotoxicity evaluation confirmed the biocompatible characteristics of the ACFs‐containing hydrogels. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Thermoresponsive self‐assembled nanovesicles based on amphiphilic triblock copolymers and their potential applications as smart drug release carriers

A series of thermoresponsive triblock copolymers, methoxy poly(ethylene oxide)‐b‐poly(ε‐caprolactone)‐b‐poly(N‐isopropylacrylamide) (mPEO‐b‐PCL‐b‐PNIPAM), with different PCL and PNIPAM block lengths, were synthesized by a combination of ring opening polymerization and reversible addition‐fragmentation chain transfer polymerization techniques. The triblock copolymers undergo self‐assembly in aqueous solutions forming stable nanovesicles of various sizes with a lipid membrane structure similar to body cells as revealed by transmission electron microscopy. The nanovesicle is thermoresponsive, that is, its size is tunable using the temperature as a switch: shrinks at a temperature above the lower critical solution temperature (LCST) and expands at a temperature below the LCST. The corresponding LCST of the triblock copolymers is adjustable by varying the PNIAM segment length as well as the PCL segment length and covers a range from 33.9 to 41.0°C in water. The diameter of nanovesicles for mPEO_3k‐b‐PCL_5k‐b‐PNIPAM_13.2k is about 177.7 nm below the LCST and 138.9 nm above the LCST, as determined by dynamic light scattering. It was demonstrated using indomethacin, a popular anti‐inflammation medicine, that the triblock copolymers can effectively act as a drug release carrier under the right human physiological conditions, that is, store the drug at a lower temperature and release it at a higher temperature, possibly targeting at the lesion sites of human body. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41361.     

Preparation and release behavior of temperature‐ and pH‐responsive chitosan material

BACKGROUND: Chitosan is a polymer with good biocompatibility which makes it promising for potential applications in the field of drug delivery. A novel kind of copolymer, P(CS‐Ma‐graft‐NIPAm), was synthesized with chitosan (CS), maleic anhydride (Ma) and N‐isopropylacrylamide (NIPAm) by grafting and copolymerization. RESULTS: The copolymers were characterized using Fourier transform infrared, ¹H NMR and ultraviolet spectroscopies, and the molecular weight and polydispersity were determined using gel permeation chromatography. The aqueous solution properties of the copolymer and the controlled delivery of coenzyme A from it were also studied. The results showed that the copolymer had temperature and pH sensitivities, and that the release of coenzyme A from the copolymer was dependent on the release medium, namely the concentration of the copolymer, pH and temperature. Higher concentrations of the copolymer absorbed more coenzyme A than lower ones. Increasing temperature accelerated coenzyme A release from the copolymer. Also, the pH of the solution had a significant impact on the release of coenzyme A. CONCLUSION: These results suggest that the novel copolymer could be used in drug delivery systems. Copyright © 2007 Society of Chemical Industry     

Hollow PUA/PSS/Au microcapsules with interdependent near‐infrared/pH/temperature multiresponsiveness

In this work, smart hollow microcapsules made of thermal‐/pH‐dual sensitive aliphatic poly(urethane‐amine) (PUA), sodium poly(styrenesulfonate) (PSS), and Au nanoparticles (AuNPs) for interdependent multi‐responsive drug delivery have been constructed by layer‐by‐layer (LbL) technique. The electrostatic interactions among PUA, PSS, and AuNPs contribute to the successful self‐assembly of hollow multilayer microcapsules. Thanks to the shrinkage of PUA above its lower critical solution temperature (LCST) and the interaction variation between PUA and PSS at different pH conditions, hollow microcapsules exhibit distinct pH‐ and thermal‐sensitive properties. Moreover, AuNPs aggregates can effectively convert light to heat upon irradiation with near‐infrared (NIR) laser and endow the hollow microcapsules with distinct NIR‐responsiveness. More importantly, the NIR‐responsive study also demonstrates that the microcapsule morphology and the corresponding NIR‐responsive drug release are strongly dependent on the pH value and temperature of the media. The results indicate that the prepared hollow PUA/PSS/Au microcapsules have the great potential to be used as a novel smart drug carrier for the remotely controllable drug delivery. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43008.     

Stimuli‐responsive molecularly imprinted hybrid polymer gel as a potential system for controlled release

The purpose of this study is to develop a stimuli‐responsive hybrid polymer gel system with an improved mechanical stability as a controlled drug delivery carrier that can undergo phase transition by the stimulation of ethanol–water mixture. For this aim, trimethoxysilane terminated poly(propylene glycol) by coupling of 3‐isocyanatopropyl‐triethoxysilane with the hydroxyl end groups of poly(propylene glycol) through urethane bonds was synthesized. Hybrid polymer gels prepared in the presence of tryptophan (Trp), as a model of drug, were characterized and gelation time of polymer network was obtained by monitoring the fluorescence emission of Trp in pre‐gel solution. Swelling, solvent uptake and release kinetic of polymer gels were evaluated depending on time. The diffusional exponents (n) and diffusion constants (k) of each gel were calculated by using the swelling kinetic data. The effect of precursors as a monomer on Trp release profile was analyzed. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42913.     

Temperature,pH, and reduction triple‐stimuli‐responsive inner‐layer crosslinked micelles as nanocarriers for controlled release

Temperature, pH, and reduction triple‐stimuli‐responsive inner‐layer crosslinked micelles as nanocarriers for drug delivery and release are designed. The well‐defined tetrablock copolymer poly(polyethylene glycol methacrylate)–poly[2‐(dimethylamino) ethyl methacrylate]–poly(N‐isopropylacrylamide)–poly(methylacrylic acid) (PPEGMA‐PDMAEMA‐PNIPAM‐PMAA) is synthesized via atom transfer radical polymerization, click chemistry, and esterolysis reaction. The tetrablock copolymer self‐assembles into noncrosslinked micelles in acidic aqueous solution. The core‐crosslinked micelles, shell‐crosslinked micelles, and shell–core dilayer‐crosslinked micelles are prepared via quaternization reaction or carbodiimide chemistry reaction. The crosslinked micelles are used as drug carriers to load doxorubicin (DOX), and the drug encapsulation efficiency with 20% feed ratio reached 59.2%, 73.1%, and 86.1%, respectively. The cumulative release rate of DOX is accelerated by single or combined stimulations. The MTT (3‐(4,5‐Dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide) assay verifies that the inner‐layer crosslinked micelles show excellent cytocompatibility, and DOX‐loaded micelles exhibit significantly higher inhibition for HepG2 cell proliferation. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46714.     

Synthesis and catalytic activity of the thermoresponsive polymers having pyrrolidine side chains as base functionalities

Optically active polymers having chiral 2‐aminomethylpyrrolidine side chains have been newly synthesized by a radical homopolymerization of the corresponding protected acrylamide monomer and copolymerization with N‐isopropylacrylamide followed by deprotection. The resulting polymers were found to be thermoresponsive showing lower critical solution temperatures (LCSTs) at 27–65°C in their aqueous solutions. The pyrrolidine side chains of the resulting thermoresponsive polymer promoted aldol reaction between cyclohexanone and p‐nitrobenzaldehyde in water, and the reaction proceeded most smoothly at its LCST. Moreover, the diastereomeric ratio (syn : anti) of the aldol adducts obtained at the reaction at 40°C was 22 : 78, whereas the diastereomeric ratio (syn : anti) was 55 : 45 at 20°C. These results indicate that the pyrrolidine side chains catalyze the aldol reactions in the relatively hydrophobic field generated by the thermoresponsive polymer at its LCST. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Polyampholyte acrylic latexes for tablet coating applications

Polyampholyte latexes can exist within a certain pH range as low‐viscosity aqueous dispersions, while upon a pH shift to the vicinity of the isoelectric point they undergo ionic coacervation. Three classes of coacervation latexes were synthesized and evaluated for their suitability for use in tablet coating applications. Pharmaceutical tablet coatings are commonly based on hydroxypropyl methyl cellulose, poly(vinyl alcohol), and acrylic polymers. Because of the high viscosity of their aqueous solutions, and to the consequent required low concentrations of the tablet coating polymers in the coating solutions to enable sufficiently low viscosity for effective spray application, the current commercial pharmaceutical tablet coating technology requires the removal of large amounts of water during the manufacturing process. In this work, films prepared from high‐solids, low‐viscosity coacervated acrylic latexes showed good hardness, very low tackiness, an excellent combination of optical properties, and very low water vapor permeability. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40049.     

Layer‐by‐layer assembly of poly(allylamine hydrochloride)/polyurethane and its loading and release behavior for methylene orange

Here, layer‐by‐layer technique was used for sequential adsorption of oppositely charged polymer poly(allylamine hydrochloride) (PAH) and polyurethane (PU) through electrostatic interaction. 10 and 10.5 bilayer films were prepared separately, methylene orange (MO) was used as a model drug to evaluate the potential ability of this multilayer film used in drug delivery system. Experimental results showed the ability of loading and release of MO from the film was significantly influenced by pH and salt concentration, the loading rate of MO was faster and larger with increasing salt concentration or decreasing pH of MO solution, the release rate of MO was faster at higher salt concentration or in alkali solution. The result also indicated that the film had a good reversibility of loading and release. PAH/PU film could be a promising drug delivery system because of its biocompatibility, biodegradation and above properties. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Synthesis and swelling behavior of pH‐responsive polyurethane/poly[2‐(diethylamino)ethyl methacrylate] hybrid materials

Polyurethane (PU)/poly[2‐(diethylamino)ethyl methacrylate] hybrids, having a chemical bond between the PU and acrylic moieties and with different compositions, were prepared by the dispersion polymerization of 2‐(diethylamino)ethyl methacrylate (DEA) in the presence of preformed PU chains with polymerizable terminal vinyl groups. The PU dispersion was synthesized according to a prepolymer mixing process by the polyaddition of isophorone diisocyanate, poly(propylene glycol), 2‐hydroxyethyl methacrylate, and dimethylol propionic acid (DMPA). Then, it was dispersed in water by the prior neutralization of the carboxylic acid groups of DMPA with triethylamine, chain‐extended with ethylenediamine. The effect of the DEA content on the swelling properties (water uptake and dynamic swelling degree) at different pHs and at 37°C was determined. The samples were also characterized by Fourier transform infrared spectroscopy and modulated differential scanning calorimetry. The experimental results indicate a higher water uptake when the DEA content was increased on the hybrid materials and a significant change in the kinetics of swelling at pH 4 compared to those at pH 7. The water content of the hydrogels depended on the DEA content, and it was inversely proportional to the pH value. The pure PU film did not show important changes over the pH range examined in this study. The synthesized hybrids were useful as drug‐delivery, pH‐sensitive matrices. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39799.     

Dual responsive polymeric bionanocomposite gel beads for controlled drug release systems

Scientists are searching potential solutions for cancer treatments as well as ways to avoid the side effects of anti‐cancer agents, via targeted drug delivery. The aim of this research is to propose dual responsive beads based on sodium alginate (SA), methylcellulose (MC), and magnetic iron oxide nanoparticles (MIONs) for controlled release of 5‐Fluorouracil (5‐FU) as model drug. The beads were prepared by the dual crosslinking of SA and MC in the presence of MIONs. The structural, thermal, morphological, magnetic characteristics as well as the release profile of 5‐FU were studied. The characterization results showed that the drug molecules and MIONs were well dispersed in the polymeric matrix. The cumulative release percentage was ca. 80% at pH = 4.2 and 40% at pH = 7.2 after 6 h. Thus, the sensitivity of beads on the pH value was verified. Moreover, the release profile exhibited reduction with an increase in the concentration of MIONs under an external magnetic field. The obtained results confirmed the dual sensitive release of 5‐FU (i.e., PH/magnetic) that can be used for the targeted and controlled drug delivery systems. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45143.     

Thermo‐responsive albumin hydrogels with LCST near the physiological temperature

This paper deals with the synthesis of thermoresponsive microspheres with proteic structure exhibiting a transition temperature close to the body temperature. The hydrogels were synthesized by free radical polymerization of methacrylate Bovine Serum Albumin (BSA‐MA) as crosslinker, and 2‐hydroxyethyl methacrylate (HEMA) and/or N‐isopropylacrylamide (NIPAAm), as hydrophilic and thermoresponsive monomers, respectively. The modification of the hydrophilic/hydrophobic balance in the polymerization feed allows to modulate the volume phase transition temperature of the macromolecular network. The hydrogels were characterized by infrared spectroscopy and thermal analyses, which showed negative thermoresponsive behavior for all compositions and, by increasing the content of the hydrophilic moieties in the network, the transition temperature was ranged from 34.2 to 36.8°C. To test the preformed materials as drug carriers, diclofenac diethyl ammonium salt was chosen and drug entrapment percent was determined. Drug release profiles, in media at different temperature, depend on the crosslinking degree and on the composition of the hydrogels. By using semiempirical equations, the release mechanism was extensively studied and the diffusional contribute evaluated. The physic‐chemical characteristics of thermoresponsive materials confirm the applicability of the microspheres as drug delivery device. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Independent control of lower critical solution temperature and swelling behavior with pH for poly(N‐isopropylacrylamide‐co‐maleic acid)

Polymer solutions that gel in response to changes in temperature and pH are of interest for various forms of drug delivery, and it is desirable to increase swelling for diffusion‐controlled release without bringing the lower critical solution temperature (LCST) above 37°C. N‐isopropylacrylamide (NIP) was polymerized with maleic acid (MAc), a diprotic acid, and acrylic acid (AAc), a monoprotic acid, to compare swelling and temperature response with changes in pH. For samples with equal acid contents and almost identical LCST responses to pH, poly(N‐isopropylacrylamide‐co‐maleic acid) (pNIP MAc) demonstrated greater swelling than poly(N‐isopropylacrylamide‐co‐acrylic acid) (pNIP AAc). The LCST increase for MAc occurred at a pH corresponding to the deprotonation of almost all of the first acid groups. Further increases in pH led to the deprotonation of the second ? COOH and only served to increase the charge concentration at a given location. These results provide strong support for the theory that LCST results largely from uninterrupted chain lengths of NIP and that swelling results from the actual charge density of acid groups along the chain. Because the use of a diprotic acid copolymer allows swelling to be decoupled from LCST, pNIP MAc may be an appropriate candidate for pH‐sensitive drug‐delivery applications. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2110–2116, 2004     

Functionalized polymeric silver nanoparticle hybrid network as a dual antimicrobe: Synthesis,characterization, and antibacterial application

The present work describes a novel method for the synthesis of silver polymer nanocomposite for the delivery of amoxicillin (AMO). Silver nanoparticles (AgNPs) were synthesized with chitosan and silver nitrate. The reaction parameters were optimized. Three‐dimensional polymeric networks were synthesized by simple free‐radical graft copolymerization. UV–visible spectroscopy, Fourier transform infrared spectroscopy, X‐ray diffraction, SEM, atomic force microscopy, dynamic light scattering, and zeta potential analysis were used for the complete characterization of the samples. Swelling studies and swelling factors were evaluated. In vitro release of AMO and AgNPs at physiological pHs was analyzed using the Peppas kinetic model to explain the drug delivery mechanism. Cytotoxicity, free‐radical scavenging, and antibacterial activities were analyzed. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43479.     

pH‐sensitive hydroxyethyl starch–doxorubicin conjugates as antitumor prodrugs with enhanced anticancer efficacy

Doxorubicin (DOX) is a widely used chemotherapeutic drug for the treatment of several types of cancers, which has limitation in clinical applications because of severe heart toxicity. Herein, to reduce the fast clearance from the blood system and the severe systemic toxicity caused by the nonspecific protein adsorption, a pH‐sensitive drug delivery system with higher drug conjugated content was prepared by conjugating DOX onto hydroxyethyl starch (HES) with a pH‐sensitive hydrazone bond. In normal physiological environment, the release of DOX conjugated onto HES was slight which could be neglected without any side effect. However, in an acidic environment mimicking the tumor microenvironment, this pH‐sensitive hydrazone linkage provided a controlled and sustained release of DOX over a period of more than 3 days. The conjugates had good biocompatibility, long circulation, and lower cytotoxicity, which could efficiently be transferred into HeLa and HepG2 cells and release the conjugated drug. Based on these promising properties, these HES–DOX conjugates outline the significant potential for future biomedical application in the controlled release of antitumor drugs. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42778.     

Synthesis,characterization, and swelling behavior of new pH‐sensitive hydrogels derived from copolymers of 2‐hydroxyethyl methacrylate and 2‐(diisopropylamino)ethylmethacrylate

The aim of this work was to synthesize and to characterize new pH‐sensitive hydrogels that can be used in the controlled release of drugs, useful for dermal treatments or ophthalmology's therapies. Copolymers containing 2‐hydroxyethyl methacrylate (HEMA) with different amounts of 2‐(diisopropylamino)ethyl methacrylate (DPA) (10 and 30 wt %) and different amounts of crosslinker agent, ethylene glycol dimethacrylate (EGDMA) (1 and 3 wt %) were prepared by bulk photo‐polymerization. The copolymers were fully characterized by using Fourier‐transform infrared (FTIR) spectra, differential scanning calorimetry, thermogravimetric analysis, UV–visible spectroscopy, and measuring water content and dynamic swelling degree. The results show that modifications in the amount of DPA and/or crosslinker in the hydrogel produce variations in the thermal properties. When adding of DPA, we observed an increase in the thermal stability and decomposition temperature, as well as a change in the mechanism of decomposition. Also a decrease in the glass transition temperature was observed with regard to the value for pure pHEMA, by the addition of DPA. The water content of the hydrogels depends on the DPA content and it is inversely proportional to both the pH value and the crosslinking degree. Pure poly‐HEMA films did not show important changes over the pH range studied in this work. The dynamic swelling curves show the overshooting effect associated with the incorporation of DPA, the pH of the solution, and the crosslinking density. On the other hand, no important variations in the optical properties were observed. The synthesized hydrogels are useful as a drug delivery pH‐sensitive matrix. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

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

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