Synthesis and characterization of pH‐sensitive and thermosensitive double hydrophilic graft copolymers

A series of poly(N‐isopropylacrylamide)‐co‐poly(N^ε‐benzyloxycarbonyl‐L ‐lysine) graft copolymers (PNIPAm‐co‐PZLLys) with different side chains (degree of polymerization, DP = 5～40) and unit ratios (from 30 to 70 mol %) were prepared via free radical polymerization, followed by cleaving benzyloxycarbonyl groups (Z groups) to obtain the double hydrophilic graft copolymer, poly(N‐isopropylacrylamide)‐co‐poly(L ‐lysine) (PNIPAm‐co‐PLLys). The pH‐ and temperature‐response properties of the graft copolymers in aqueous solution were studied. The experimental results indicate L15‐N30 and L15N‐70, that is, the PNIPAm‐co‐PLLys having the poly(L ‐lysine) of DP = 15 as side chains as well as 30 and 70 mol %, respectively, of PNIPAm as backbone, have coil‐to‐helix transitions from pH 6 to pH 12 at room temperature and form uniform nanoscale micelle‐like dispersions in aqueous solution at pH 12. The graft copolymers also could form uniform and nanoscale micelle‐like structures at 50 °C in pH 6 buffer solution due to slightly polymer aggregation. With temperature and pH increased, both the deprotonated PLLys side chains and PNIPAm backbone become hydrophobic, leading to polymer precipitation. These results illustrate that a double tunable hydrophilic graft copolymer had been successfully synthesized via a simple radical polymerization, and could form micelles without serious polymer aggregation at a lower pH and a higher temperature. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Hairy polymeric nanocapsules with ph‐responsive shell and thermoresponsive brushes: Tunable permeability for controlled release of water‐soluble drugs

The hairy poly(methacrylic acid‐co‐divinylbenzene)‐g‐poly(N‐isopropylacrylamide) (P(MAA‐co‐DVB)‐g‐PNIPAm) nanocapsules with pH‐responsive P(MAA‐co‐DVB) inner shell and temperature‐responsive PNIPAm brushes were prepared by combined distillation–precipitation copolymerization and surface thiol‐ene click grafting reaction using 3‐(trimethoxysilyl)propyl methacrylate‐modified silica (SiO₂‐MPS) nanospheres as a sacrificial core material. The well‐defined PNIPAm was synthesized by a reversible addition fragmentation chain transfer (RAFT) polymerization. The chain end was converted to a thiol by chemical reduction. The PNIPAm was integrated into the nanocapsules via thiol‐ene click reaction. The surface thiol‐ene click reaction conduced to tunable grafting density of PNIPAm brushes. The grafting densities decreased from 0.70 chains nm^?2 to 0.15 chains nm^?2 with increasing the molecular weight of grafted PNIPAm chains. Using water soluble doxorubicin hydrochloride (DOX·HCl) as a model molecular, the tunable shell permeability of the nanocapsule was investigated in detail. The permeability constant can be tuned by controlling the thickness of the P(MAA‐co‐DVB) inner shell, the grafting density of PNIPAm brushes, and the environmental pH and temperature. The tunable shell permeability of these nanocapsules results in the release of the loaded guest molecules with manipulable releasing kinetics. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2202–2216     

Synthesis and characterization of well‐defined,amphiphilic poly(N‐isopropylacrylamide)‐ b‐[2‐hydroxyethyl methacrylate‐poly(ϵ‐caprolactone)]n graft copolymers by RAFT polymerization and macromonomer method

The well‐defined, thermosensitive and biodegradable graft copolymers, poly(N‐isopropylacrylamide)‐b‐[2‐hydroxyethyl methacrylate‐poly(ε‐caprolactone)]_n (PNIPAAm‐b‐(HEMA‐PCL)_n) (n = 3 or 9), were synthesized by combining reversible addition‐fragmentation chain transfer polymerization and macromonomer method. The copolymers were able to self‐assemble into micelles in water with low critical micellar concentration and demonstrated temperature sensitivity with a lower critical solution temperature at around 36 °C. Transmission electron microscopy shows that the micelles exhibit a nanosized spherical morphology within a size range of 30–100 nm. The PNIPAAm‐b‐(HEMA‐PCL)₃ copolymer exhibited biodegradation and low cytotoxicity. The paclitaxel‐loaded PNIPAAm‐b‐(HEMA‐PCL)₃ micelles displayed thermosensitive controlled release behavior, which indicates potential as drug carriers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5354–5364, 2007     

Synthesis,self‐assembly,and thermosensitive properties of ethyl cellulose‐g‐P(PEGMA) amphiphilic copolymers

Ethyl cellulose graft poly(poly(ethylene glycol) methyl ether methacrylate) (EC‐g‐P(PEGMA)) amphiphilic copolymers were synthesized via atom transfer radical polymerization (ATRP) and characterized by FTIR, ¹H NMR, and gel permeation chromatography. Reaction kinetics analysis indicated that the graft copolymerization is living and controllable. The self‐assembly and thermosensitive property of the obtained EC‐g‐P(PEGMA) amphiphilic copolymers in water were investigated by dynamic light scattering, transmission electron microscopy, and transmittance. It was found that the EC‐g‐P(PEGMA) amphiphilic copolymers can self‐assemble into spherical micelles in water. The size of the micelles increases with the increase of the side chain length. The spherical micelles show thermosensitive properties with a lower critical solution temperature around 65 °C, which almost independent on the graft density and the length of the side chains. The obtained EC‐g‐P(PEGMA) graft copolymers have both the unique properties of poly(ethylene glycol) and cellulose, which may have the potential applications in biomedicine and biotechnology. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 46: 6907–6915, 2008     

Novel thermo‐responsive self‐assembly micelles from a double brush‐shaped PNIPAM‐g‐(PA‐b‐PEG‐b‐PA)‐g‐PNIPAM block copolymer with PNIPAM polymers as side chains

A novel double brush‐shaped copolymer with amphiphilic polyacrylate‐b‐poly(ethylene glycol)‐b‐poly acrylate copolymer (PA‐b‐PEG‐b‐PA) as a backbone and thermosensitive poly(N‐isopropylacrylamide) (PNIPAM) long side chains at both ends of the PEG was synthesized via an atom transfer radical polymerization (ATRP) route, and the structure was confirmed by FTIR, ¹H NMR, and SEC. The thermosensitive self‐assembly behavior was examined via UV‐vis, TEM, DLS, and surface tension measurements, etc. The self‐assembled micelles, with low critical solution temperatures (LCST) of 34–38 ^°C, form irregular fusiform and/or spherical morphologies with single, double, and petaling cores in aqueous solution at room temperature, while above the LCST the micelles took on more regular and smooth spherical shapes with diameter ranges from 45 to 100 nm. The micelle exhibits high stabilities even in simulated physiological media, with low critical micellization concentration (CMC) up to 5.50, 4.89, and 5.05 mg L^?1 in aqueous solution, pH 1.4 and 7.4 PBS solutions, respectively. The TEM and DLS determination reveled that the copolymer micelle had broad size distribution below its LCST while it produces narrow and homogeneous size above the LCST. The cytotoxicity was investigated by MTT assays to elucidate the application potential of the as‐prepared block polymer brushes as drug controlled release vehicles. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Fabrication of thermosensitive PCL‐PNIPAAm‐PCL triblock copolymeric micelles for drug delivery

A series of thermosensitive ABA type triblock poly(ε‐caprolactone)‐b‐poly(N‐isopropylacrylamide)‐b‐poly(ε‐caprolactone) (PCL‐PNIPAAm‐PCL) copolymers with different molecular weights were synthesized by the combination of ring opening polymerization and reversible addition‐fragmentation chain transfer (RAFT) polymerization. The critical micelle concentrations (CMCs) of the resulted four triblock copolymers in aqueous solution were determined to be 33.8, 39.8, 35.5, and 41.7 mg/L, respectively, by fluorescence spectroscopy using pyrene as a fluorescence probe. Optical absorption measurements showed that the lower critical solution temperatures (LCSTs) of the copolymers were 35.8, 36.2, 35.2, and 36.2 °C, respectively, in distilled water, and 33.9, 34.2, 33.3, 34.6 °C, respectively, in PBS (pH = 6.8, I = 0.1). Transmission electron microscopy (TEM) showed that the self‐assembled micelles exhibited a well‐defined spherical shape with diameter of around 100 nm. The drug‐loaded PCL‐PNIPAAm‐PCL micelles displayed thermosensitive controlled release behaviors. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3048–3057, 2008     

The Formation of Biodegradable Polymeric Micelles from Newly Synthesized Poly(aspartic acid)‐block‐Polylactide AB‐Type Diblock Copolymers

Summary: A poly(aspartic acid)‐block‐polylactide (PAsp‐block‐PLA) diblock copolymer was synthesized through the polymerization of β‐benzyl‐L ‐aspartate‐N‐carboxyanhydride [Asp(OBzl)‐NCA] with amino‐terminating polylactide (NH₂‐PLA) as a macroinitiator. The chain length of the PAsp segment could be easily controlled by changing the monomer/initiator ratio. Dynamic light scattering measurements of PAsp‐block‐PLA aqueous solutions revealed the formation of polymeric micelles. Changes in the micelles as a function of pH were investigated.

The structure and formation of micelles of the poly(aspartic acid)‐block‐polylactide (PAsp‐block‐PLA) diblock copolymers synthesized here.     

Amphiphilic Block‐Graft Copolymers Poly(ethylene glycol)‐b‐(polycarbonates‐g‐palmitate) Prepared via the Combination of Ring‐Opening Polymerization and Click Chemistry

Amphiphilic block‐graft copolymers mPEG‐b‐P(DTC‐ADTC‐g‐Pal) were synthesized by ring‐opening polymerization of 2,2‐dimethyltrimethylene carbonate (DTC) and 2,2‐bis(azidomethyl)trimethylene carbonate (ADTC) with poly(ethylene glycol) monomethyl ether (mPEG) as an initiator, followed by the click reaction of propargyl palmitate and the pendant azido groups on the polymer chains. Stable micelle solutions of the amphiphilic block‐graft copolymers could be prepared by adding water to a THF solution of the polymer followed by the removal of the organic solvent by dialysis. Dynamic light scattering measurements showed that the micelles had a narrow size distribution. Transmission electron microscopy images displayed that the micelles were in spherical shape. The grafted structure could enhance the interaction of polymer chains with drug molecules and improve the drug‐loading capacity and entrapment efficiency. Further, the amphiphilic block‐graft copolymers mPEG‐b‐P(DTC‐ADTC‐g‐Pal) were low cytotoxic and had more sustained drug release behavior. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Synthesis and supramolecular self‐assembly of thermosensitive amphiphilic star copolymers based on a hyperbranched polyether core

A novel amphiphilic thermosensitive star copolymer with a hydrophobic hyperbranched poly (3‐ethyl‐3‐(hydroxymethyl)oxetane) (HBPO) core and many hydrophilic poly(2‐(dimethylamino) ethyl methacrylate) (PDMAEMA) arms was synthesized and used as the precursor for the aqueous solution self‐assembly. All the copolymers directly aggregated into core–shell unimolecular micelles (around 10 nm) and size‐controllable large multimolecular micelles (around 100 nm) in water at room temperature, according to pyrene probe fluorescence spectrometry and ¹H NMR, TEM, and DLS measurements. The star copolymers also underwent sharp, thermosensitive phase transitions at a lower critical solution temperature (LCST), which were proved to be originated from the secondary aggregation of the large micelles driven by increasing hydrophobic interaction due to the dehydration of PDMAEMA shells on heating. A quantitative variable temperature NMR analysis method was designed by using potassium hydrogen phthalate as an external standard and displayed great potential to evaluate the LCST transition at the molecular level. The drug loading and temperature‐dependent release properties of HBPO‐star‐PDMAEMA micelles were also investigated by using indomethacin as a model drug. The indomethacin‐loaded micelles displayed a rapid drug release at a temperature around LCST. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 668–681, 2008     

Construction of temperature responsive hybrid crosslinked self‐assemblies based on PEG‐b‐P(MMA‐co‐MPMA)‐b‐PNIPAAm triblock copolymer: ATRP synthesis and thermoinduced association behavior

A novel amphiphilic thermosensitive poly(ethylene glycol)₄₅‐b‐poly(methyl methacrylate₄₆‐co‐3‐(trimethoxysilyl)propyl methacrylate)₂‐b‐poly(N‐isopropylacrylamide)₄₂₉ (PEG₄₅‐b‐P(MMA₄₆‐co‐MPMA₂)‐b‐PNIPAAm₄₂₉) triblock copolymer was synthesized via consecutive atom transfer radical polymerization techniques. The thermoinduced association behavior of the resulting triblock copolymers in aqueous medium was further investigated in detail by ¹H NMR, transmission electron microscopy, and dynamic light scattering. The results showed that at the temperature (25 °C) below the LCST, PEG₄₅‐b‐P(MMA₄₆‐co‐MPMA₂)‐b‐PNIPAAm₄₂₉ triblock copolymers self‐assembled into the core crosslinked micelles with the hydrophobic P(MMA‐co‐MPMA) block constructing a dense core, protected by the mixed soluble PEG and PNIPAAm chains acting as a hydrophilic shell simultaneously. With an increase in temperature, the resulting core‐shell micelles converted into a new type of micelles with the hydrophilic PEG chains stretching out from the hydrophobic core through the collapsed PNIPAAm shell. On the other hand, at the temperature (40 °C) above the LCST, such triblock copolymers formed the crosslinked vesicles with the hydrophobic PNIPAAm and P(MMA‐co‐MPMA) blocks constructing a membrane core and the soluble PEG chains building the hydrophilic lumen and the shell. On further decreasing the temperature, the resulting vesicles underwent transformation from the shrunken to the expanded status, leading to the formation of swollen vesicles with enlarged size. This study is believed to present the first formation of two types of hybrid crosslinked self‐assemblies by thermoinduced regulation. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Tunable Smart Surface of Gold Nanoparticles Achieved by Light‐Controlled Molecular Recognition Effection

Thermosensitive poly(N‐isopropylacrylamide) (PNIPAm)‐coated gold nanoparticles (AuNPs) were prepared by self‐assembly of the azobenzene‐terminated PNIPAm on the surface of the α‐cyclodextrin (α‐CD)‐capped AuNPs via the host–guest molecular recognition between α‐CD and azobenzene. Reversible attachment–detachment of azobenzene‐terminated PNIPAm on the surface of α‐CD‐capped AuNPs was achieved when subjected to visible and UV light irradiation alternately, which endowed thermosensitive AuNPs with tunable smart properties.

     

Thermosensitive and control release behavior of poly (N‐isopropylacrylamide‐co‐acrylic acid) latex particles

In this work, poly(N‐isopropylacrylamide‐co‐acrylic acid) (poly(NIPAAm‐AA)) copolymer latex particles (microgels) were synthesized by the method of soapless emulsion polymerization. Poly(NIPAAm‐AA) copolymer microgels have the property of being thermosensitive. The concentration of acrylic acid (AA) and crosslinking agent N,N′‐methylenebisacrylamide were important factors to influence the lower critical solution temperature (LCST) of poly(NIPAAm‐AA) microgels. The effects of AA and crosslinking agent on the swelling behavior of poly(NIPAAm‐AA) microgels were also studied. The poly(NIPAAm‐AA) copolymer microgels were then used as a thermosensitive drug carrier to load caffeine. The effects of concentration of AA and crosslinking agent on the control release of caffeine were investigated. How the AA content and crosslinking agent influenced the morphology and LCST of the microgels was discussed in detail. The relationship of morphology, swelling, and control release behavior of these thermosensitive microgels was established. A new scheme was proposed to interpret the control release of the microgels with different morphological structures. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5734–5741, 2008     

PPEGMEA‐g‐PDEAEMA: Double hydrophilic double‐grafted copolymer stimuli‐responsive to both pH and salinity

A series of well‐defined double hydrophilic double‐grafted copolymers, consisting of polyacrylate backbone, hydrophilic poly(2‐(diethylamino)ethyl methacrylate) and poly(ethylene glycol) side chains, were synthesized by successive atom transfer radical polymerization. The backbone, poly[poly(ethylene glycol) methyl ether acrylate] (PPEGMEA) comb copolymer, was firstly prepared by ATRP of PEGMEA macromonomer via the grafting‐through route followed by reacting with lithium diisopropylamide and 2‐bromopropionyl chloride to give PPEGMEA‐Br macroinitiator of ATRP. Finally, poly[poly(ethylene glycol) methyl ether acrylate]‐g‐poly(2‐(diethylamino)ethyl methacrylate) graft copolymers were synthesized by ATRP of 2‐(diethylamino)ethyl methacrylate using PPEGMEA‐Br macroinitiator via the grafting‐from route. Poly(2‐(diethylamino)ethyl methacrylate) side chains were connected to polyacrylate backbone through stable C? C bonds instead of ester connections, which is tolerant of both acidic and basic environment. The molecular weights of both backbone and side chains were controllable and the molecular weight distributions kept relatively narrow (M_w/M_n ≤ 1.39). The results of fluorescence spectroscopy, dynamic laser light scattering and transmission electron microscopy showed this double hydrophilic copolymer was stimuli‐responsive to both pH and salinity. It can aggregate to form reversible micelles in basic surroundings which can be conveniently dissociated with the addition of salt at room temperature. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3142–3153, 2009     

Self‐assembly of a triblock terpolymer mediated by hydrogen‐bonded complexes

A poly(methyl methacrylate)‐block‐poly(4‐vinylpyridine)‐block‐polystyrene (PMMA‐b‐P4VP‐b‐PS) triblock terpolymer is synthesized by ATRP to study its self‐assembly with PAA in organic solvents. The self‐assembly behavior of this system is compared with the one of a mixture of two diblocks, namely polystyrene‐block‐poly(4‐vinylpyridine) (PS‐b‐P4VP) and poly(methyl methacrylate)‐block‐poly(methacrylic acid) (PMMA‐b‐PMAA). For both systems, formation of hydrogen‐bonded complexes between the P4VP and PMAA or PAA blocks occurs. These complexes become insoluble in the solvent used and micelles with a P4VP/P(M)AA complexes core surrounded by PS and PMMA coronal chains are obtained in both cases. These micelles are analyzed by DLS and TEM. Spherical micelles are formed for both systems but the hydrodynamic radii obtained for the two types of micelles are different. Indeed, the micelles formed by the PMMA‐b‐P4VP‐b‐PS + PAA system are smaller than those observed for the PS‐b‐P4VP + PMMA‐b‐PMAA system. Finally, the effect of the molar ratio of the P4VP/PMAA complexing blocks is investigated. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 459–467     

Peptide‐poly(tert‐butyl methacrylate) conjugate into composite micelles in organic solvents versus peptide‐poly(methacrylic acid) conjugate into spherical and worm‐like micelles in water: Synthesis and self‐assembly

Peptide–polymer conjugates are versatile class of biomaterials composed of a peptide block covalently linked with a synthetic polymer block. This report demonstrates the synthesis of peptide‐poly(tert‐butyl methacrylate) (Peptide‐P^tBMA) conjugates of varying molecular weights via a “grafting from” atom transfer radical polymerization (ATRP) technique using as‐synthesized peptide‐based initiator in toluene. Peptide‐P^tBMA conjugate is soluble in many organic solvents and undergoes self‐assembly into micro/nanospheres in DMF/THF as observed from both FESEM and DLS results. The conjugate micro/nanospheres are nothing but the composite micelles formed by the secondary aggregation of primary micelles generated initially in these organic solvents. The hydrolysis of tert‐butyl groups of Peptide‐P^tBMA conjugate leads to the formation of peptide‐poly(methacrylic acid) (Peptide‐PMA) conjugate. The circular dichroism (CD) analysis exhibits the presence of β‐sheet conformation of peptide moiety in synthesized conjugates. The formed Peptide‐PMA conjugate is soluble in water and owing to its amphiphilic character, the conjugate molecules self‐assemble into spherical micelles as well as worm‐like micelles upon increasing the concentration of conjugate in water. However, the sodium salt of Peptide‐PMA conjugates (Peptide‐PMAS) self‐assembles into only spherical swollen micelles in water at higher (pH ～10). The critical aggregation concentrations (CACs) of both Peptide‐PMA and Peptide‐PMAS micelles are measured by fluorescence spectroscopy. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3019–3031     

Synthesis of poly(L‐lysine)‐graft‐polyesters through Michael addition and their self‐assemblies in aqueous solutions

A series of poly(L ‐lysine)s grafted with aliphatic polyesters, poly(L ‐lysine)‐graft‐poly(L ‐lactide) (PLy‐g‐PLLA) and poly(L ‐lysine)‐graft‐poly(?‐caprolactone) (PLy‐ g‐PCL), were synthesized through the Michael addition of poly(L ‐lysine) and maleimido‐terminated poly(L ‐lactide) or poly(?‐caprolactone). The graft density of the polyesters could be adjusted by the variation of the feed ratio of poly(L ‐lysine) to the maleimido‐terminated polyesters. IR spectra of PLy‐g‐PCL showed that the graft copolymers adopted an α‐helix conformation in the solid state. Differential scanning calorimetry measurements of the two kinds of graft copolymers indicated that the glass transition temperature of PLy‐g‐PLLA and the melting temperature of PLy‐g‐PCL increased with the increasing graft density of the polyesters on the backbone of poly(L ‐lysine). Circular dichroism analysis of PLy‐g‐PCL in water demonstrated that the graft copolymer existed in a random‐coil conformation at pH 6 and as an α‐helix at pH 9. In addition, PLy‐g‐PCL was found to form micelles to vesicles in an aqueous medium with the increasing graft density of poly(?‐caprolactone). © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1889–1898, 2007     

Synthesis,micelle formation,and bulk properties of poly(ethylene glycol)‐b‐poly(pentafluorostyrene)‐g‐polyhedral oligomeric silsesquioxane amphiphilic hybrid copolymers

The synthesis, micelle formation, and bulk properties of semifluorinated amphiphilic poly(ethylene glycol)‐b‐poly(pentafluorostyrene)‐g‐cubic polyhedral oligomeric silsesquioxane (PEG‐b‐PPFS‐g‐POSS) hybrid copolymers is reported. The synthesis of amphiphilic PEG‐b‐PPFS block copolymers are achieved using atom transfer radical polymerization (ATRP) at 100 °C in trifluorotoluene using modified poly(ethylene glycol) as a macroinitiator. Subsequently, a proportion of the reactive para‐F functionality on the pentafluorostyrene units was replaced with aminopropylisobutyl POSS through aromatic nucleophilic substitution reactions. The products were fully characterized by ¹H‐NMR and GPC. The products, PEG‐b‐PPFS and PEG‐b‐PPFS‐g‐POSS, were subsequently self‐assembled in aqueous solutions to form micellar structures. The critical micelle concentrations (cmc) were estimated using two different techniques: fluorescence spectroscopy and dynamic light scattering (DLS). The cmc was found to decrease concomitantly with the number of POSS particles grafted per copolymer chain. The hydrodynamic particle sizes (R_h) of the micelles, calculated from DLS data, increase as the number of POSS molecules grafted per copolymer chain increases. For example, R_h increased from ～60 nm for PEG‐b‐PPFS to ～80 nm for PEG‐b‐PPFS‐g‐POSS25 (25 is the average number of POSS particles grafted copolymer chain). Static light scattering (SLS) data confirm that the formation of larger micelles by higher POSS containing copolymers results from higher aggregation numbers (N_agg), caused by increased hydrophobicity. The R_g/R_h values, where R_g is the radius of gyration calculated from SLS data, are consistent with a spherical particle model having a core‐shell structure. Thermal characterization by differential scanning calorimetry (DSC) reveals that the grafted POSS acts as a plasticizer; the glass transition temperature (T_g) of the PPFS block in the copolymer decreases significantly with increasing POSS content. Finally, the rhombohedral crystal structure of POSS in PEG‐b‐PPFS‐g‐POSS was verified by wide angle X‐ray diffraction measurements. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 152–163, 2010     

Synthesis and characteristics of poly(methacrylic acid‐co‐N‐isopropylacrylamide) thermosensitive composite hollow latex particles and their application as drug carriers

In this work, the poly(methacrylic acid‐co‐N‐isopropylacrylamide) thermosensitive composite hollow latex particles was synthesized by a three‐step reaction. The first step was to synthesize the poly(methyl methacrylate‐co‐methacrylic acid) (poly(MMA‐MAA)) copolymer latex particles by the method of soapless emulsion polymerization. The second step was to polymerize methacrylic acid (MAA), N‐isopropylacrylamide (NIPAAm), and N,N′‐methylenebisacrylamide in the presence of poly(MMA‐MAA) latex particles to form the linear poly(methyl methacrylate‐co‐methacrylic acid)/crosslinking poly(methacrylic acid‐co‐N‐isopropylacrylamide) (poly(MMA‐MAA)/poly(MAA‐NIPAAm)) core–shell latex particles. In the third step, the core–shell latex particles were heated in the presence of ammonia solution to form the crosslinking poly(MAA‐NIPAAm) thermosensitive hollow latex particles. The morphologies of poly(MMA‐MAA)/poly(MAA‐NIPAAm) core–shell latex particles and poly(MAA‐NIPAAm) hollow latex particles were observed. The influences of crosslinking agent and shell composition on the lower critical solution temperature of poly(MMA‐MAA)/poly(MAA‐NIPAAm) core–shell latex particles and poly(MAA‐NIPAAm) hollow latex particles were, respectively, studied. Besides, the poly(MAA‐NIPAAm) thermosensitive hollow latex particles were used as carriers to load with the model drug, caffeine. The effect of various variables on the amount of caffeine loading and the efficiency of caffeine release was investigated. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 5203–5214     

Synthesis and characteristics of poly(methyl methacrylate‐co‐methacrylic acid)/poly(methacrylic acid‐co‐N‐isopropylacrylamide) thermosensitive semi‐hollow latex particles and their application to drug carriers

In this work, the poly(methyl methacrylate‐co‐methacrylic acid)/poly(methacrylic acid‐co‐N‐isopropylacrylamide) thermosensitive composite semi‐hollow latex particles was synthesized by three processes. The first process was to synthesize the poly(methyl methacrylate‐co‐methacrylic acid) (poly (MMA‐MAA)) copolymer latex particles by the method of soapless emulsion polymerization. The second process was to polymerize methacrylic acid (MAA), N‐isopropylacrylamide (NIPAAm), and crosslinking agent, N,N′‐methylenebisacrylamide, in the presence of poly(MMA‐MAA) latex particles to form the linear poly(methyl methacrylate‐co‐methacrylic acid)/crosslinking poly(methacrylic acid‐co‐N‐isopropylacrylamide) (poly(MMA‐MAA)/poly(MAA‐NIPAAm)) core–shell latex particles with solid structure. In the third process, part of the linear poly(MMA‐MAA) core of core–shell latex particles was dissolved by ammonia to form the poly(MMA‐MAA)/poly(MAA‐NIPAAm) thermosensitive semi‐hollow latex particles. The morphologies of the semi‐hollow latex particles show that there is a hollow zone between the linear poly(MMA‐MAA) core and the crosslinked poly(MAA‐NIPAAm) shell. The crosslinking agent and shell composition significantly influenced the lower critical solution temperature of poly(MMA‐MAA)/poly(MAA‐NIPAAm) semi‐hollow latex particles. Besides, the poly(MMA‐MAA)/poly(MAA‐NIPAAm) thermosensitive semi‐hollow latex particles were used as carriers to load with the model drug, caffeine. The processes of caffeine loaded into the semi‐hollow latex particles appeared four situations, which was different from that of solid latex particles. In addition, the phenomenon of caffeine released from the semi‐hollow latex particles was obviously different from that of solid latex particles. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3441–3451     

Noncovalently connected micelles based on a β‐cyclodextrin‐containing polymer and adamantane end‐capped poly(ε‐caprolactone) via host–guest interactions

New random copolymers, poly(N‐vinyl‐2‐pyrrolidone‐co‐mono‐6‐deoxy‐6‐methacrylate ethylamino‐β‐cyclodextrin) (PnvpCD) bearing pendent β‐cyclodextrin (CD) groups were synthesized. PnvpCD formed soluble graft‐like polymer complex with adamantane (AD) end‐capped poly(ε‐caprolactone) (PclAD) in their common solvent N‐methyl‐2‐pyrrolidone driven by the inclusion interactions between the CD and AD groups. The formation of the graft complex has been confirmed by viscometry, dynamic light scattering (DLS), and isothermal titration calorimeter. The graft complex self‐assembled further into noncovalently connected micelles in water, which is a selective solvent for the main chain PnvpCD. Transmission electron microscopy, DLS, and atomic force microscopy have been used to investigate the structure and morphology of the resultant micelles. A unique “multicore” structure of the micelles, in which small PclAD domains scattered within the micelles, was obtained under nonequilibrium conditions in the preparation. However, the micelles prepared in a condition close to equilibrium possess an ordinary core‐shell structure. In both cases, the core and shell are believed to be connected by the AD‐CD inclusion complexation. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4267–4278, 2009