An efficient approach to synthesize polysaccharides‐graft‐poly(p‐dioxanone) copolymers as potential drug carriers

Starch and poly(p‐dioxanone) (PPDO) are the natural and synthetic biodegradable and biocompatible polymers, respectively. Their copolymers can find extensive applications in biomedical materials. However, it is very difficult to synthesize starch‐graft‐PPDO copolymers in common organic solvents with very good solubility. In this article, well‐defined polysaccharides‐graft‐poly(p‐dioxanone) (SA_n‐PPDO) copolymers were successfully synthesized via the ring‐opening polymerization of p‐dioxanone (PDO) with an acetylated starch (SA) initiator and a Sn(Oct)₂ catalyst in bulk. The copolymers were characterized via Fourier transform infrared spectroscopy, ¹H NMR, gel permeation chromatography, thermogravimetric analysis (TG), differential scanning calorimetry, and wide angle x‐ray diffraction. The in vitro degradation results showed that the introduction of SA segments into the backbone chains of the copolymers led to an enhancement of the degradation rate, and the degradation rate of SA_n‐PPDO increased with the increase of SA wt %. Microspheres with an average volume diameter of 20 μm, which will have potential applications in controlled release of drugs, were successfully prepared by using these new copolymers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5344–5353, 2009     

Physicochemical characterization and drug release properties of PDMAEMA/OSA Semi‐IPN hydrogels with microporous structure

A new poly(2‐(dimethylamino) ethyl methacrylate)/oxidized sodium alginate (PDMAEMA) semi‐interpenetrating network (Semi‐IPN) hydrogel with microporous structure was prepared by using PDMAEMA microgels as an additive during the polymerization/crosslinking process. The interior morphology characterized by scanning electron microscopy showed the Semi‐IPN hydrogels have different pore sizes by changing the amount of microgels. The hydrogels were also characterized by using Fourier transform infrared and DSC. The swelling behaviors of hydrogels indicated that the hydrogels have excellent pH and temperature sensitivity. Bovine serum albumin was entrapped in the hydrogels and the in vitro drug release profiles were established in different buffer solutions at various temperatures. The release behaviors of the model drug were dependent on the pore size of the hydrogels and environmental temperature/pH, which suggested that these materials have potential application as intelligent drug carriers. Copyright © 2011 John Wiley & Sons, Ltd.     

Stimuli‐responsive amphiphilic PDMAEMA‐b‐PLMA copolymers and their cationic and zwitterionic analogs

In this work, the synthesis and characterization of novel amphiphilic diblock copolymers of poly(2‐dimethylamino ethyl methacrylate)‐b‐poly(lauryl methacrylate), PDMAEMA‐b‐PLMA, using the reversible addition‐fragmentation chain transfer (RAFT) polymerization technique, are reported. The diblocks were successfully derivatized to cationic and zwitterionic block polyelectrolytes by quaternization and sulfobetainization of the PDMAEMA block, respectively. Furthermore, their molecular and physicochemical characterization was performed by using characterization techniques such as NMR and FTIR, size exclusion chromatography, light scattering techniques, and transmission electron microscopy. The structure of the diblock micelles, their behavior, and properties in aqueous solution were investigated under the effect of pH, temperature, and ionic strength, as PDMAEMA and its derivatives are stimuli‐responsive polymers and exhibit responses to variations of at least one of these physicochemical parameters. These new families of stimuli‐responsive block copolymers respond to changes of their environment giving interesting nanostructures, behavioral motifs, and properties, rendering them useful as nanocarriers for drug delivery and gene therapy. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 598–610     

Synthesis and characterization of block copolymers from 2‐vinylnaphthalene by anionic polymerization

The anionic polymerization of 2‐vinylnaphthalene (2VN) has been studied in tetrahydrofuran (THF) at ?78 °C and in toluene at 40 °C. 2VN polymerization in THF, toluene, or toluene/THF (99:1 v/v) initiated by sec‐butyllithium (sBuLi) indicates living characteristics, affording polymers with predefined molecular weights and narrow molecular weight distributions. Block copolymers of 2VN with methyl methacrylate (MMA) and tert‐butyl acrylate (tBA) have been synthesized successfully by sequential monomer addition in THF at ?78 °C initiated by an adduct of sBuLi–LiCl. The crossover propagation from poly(2‐vinylnaphthyllithium) (P2VN) macroanions to MMA and tBA appears to be living, the molecular weight and composition can be predicted, and the molecular weight distribution of the resulting block copolymer is narrow (weight‐average molecular/number‐average molecular weight < 1.3). Block copolymers with different chain lengths for the P2VN segment can easily be prepared by variations in the monomer ratios. The block copolymerization of 2VN with hexamethylcyclotrisiloxane also results in a block copolymer of P2VN and poly(dimethylsiloxane) (PDMS) contaminated with a significant amount of homo‐PDMS. Poly(2VN‐b‐nBA) (where nBA is n‐butyl acrylate) has also been prepared by the transesterification reaction of the poly(2VN‐b‐tBA) block copolymer. Size exclusion chromatography, Fourier transform infrared, and ¹H NMR measurements indicate that the resulting polymers have the required architecture. The corresponding amphiphilic block copolymer of poly(2VN‐b‐AA) (where AA is acrylic acid) has been synthesized by acidic hydrolysis of the ester group of tert‐butyl from the poly(2VN‐b‐tBA) copolymer. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4387–4397, 2002     

Biodegradable electrospun mat: Novel block copolymer of poly (p‐dioxanone‐co‐L‐lactide)‐block‐poly(ethylene glycol)

Ultrafine fibers of a laboratory‐synthesized new biodegradable poly(p‐dioxanone‐co‐L ‐lactide)‐block‐poly(ethylene glycol) copolymer were electrospun from solution and collected as a nonwoven mat. The structure and morphology of the electrospun membrane were investigated by scanning electron microscopy, differential scanning calorimetry (DSC), wide‐angle X‐ray diffraction (WAXD), and a mercury porosimeter. Solutions of the copolymer, ranging in the lactide fraction from 60 to 80 mol % in copolymer composition, were readily electrospun at room temperature from solutions up to 20 wt % in methylene chloride. We demonstrate the ability to control the fiber diameter of the copolymer as a function of solution concentration with dimethylformamide as a cosolvent. DSC and WAXD results showed the relatively poor crystallinity of the electrospun copolymer fiber. Electrospun copolymer membrane was applied for the hydrolytic degradation in phosphate buffer solution (pH = 7.5) at 37 °C. Preliminary results of the hydrolytic degradation demonstrated the degradation rate of the electrospun membrane was slower than that of the corresponding copolymers of cast film. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1955–1964, 2003     

Amphiphilic block copolymers based on poly(2-acryloyloxyethyl phosphorylcholine) prepared via RAFT polymerisation as biocompatible nanocontainers

Amphiphilic block copolymers composed of poly(butyl acrylate) and poly(2-acryloyloxyethyl phosphorylcholine) have been prepared using reversible addition fragmentation transfer (RAFT) polymerisation. The conversion of the polymerisation was determined using online FT NIR spectroscopy. NMR spectroscopy was used not only to support the results obtained from FT NIR spectroscopy but also prove the formation of micelles. Due to the strong aggregation tendency of these block copolymers and the resulting difficulties concerning the molecular weight analysis test experiments were carried out replacing poly(2-acryloyloxyethyl phosphorylcholine) with poly(2-hydroxyethyl acrylate). Micelle size and the aggregation behaviour were investigated using dynamic light scattering. The sizes of the nanocontainers obtained were found to be influenced by the block length as well as the solvent leading to micelles in the range between 40 and 160 nm. The toxicity of the RAFT agent used was then analysed by cell growth inhibition tests.     

Novel block ionomers II. Synthesis and characterization of polyisobutylene‐based block cationomers

Various novel block cationomers consisting of polyisobutylene (PIB) and poly[2‐(dimethylamino)ethyl methacrylate] (PDMAEMA) segments were synthesized and characterized. The specific targets were various molecular weight diblocks (PIB‐b‐PDMAEMA⁺) and triblocks (PDMAEMA⁺‐b‐PIB‐b‐PDMAEMA⁺), with the PIB blocks in the DP_n = 50–200 range (number‐average molecular weight = 3,000–9000 g/mol) connected to blocks of PDMAEMA⁺ cations in the DP_n = 5–20 range (where DP is the number‐average degree of polymerization). The overall synthetic strategy for the preparation of these block cationomers had four steps: (1) synthesis by living cationic polymerization of mono‐ and diallyltelechelic polyisobutylenes, (2) end‐group transformation to obtain PIBs fitted with termini capable of mediating the atom transfer radical polymerization (ATRP) of DMAEMA, (3) ATRP of DMAEMA, and (4) quaternization of PDMAEMA to PDMAEMA ⁺I^? by CH₃I. Scheme 1 shows the microarchitecture and outlines the synthesis route. Kinetic and model experiments provided guidance for developing convenient synthesis methods. The microarchitecture of PIB–PDMAEMA di‐ and triblocks and the corresponding block cationomers were confirmed by ¹H NMR and FTIR spectroscopy and solubility studies. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3679–3691, 2002     

Preparation and characterization of biodegradable poly(trimethylenecarbonate‐ε‐caprolactone)‐block‐poly(p‐dioxanone) copolymers

A series of poly(trimethylenecarbonate‐ε‐caprolactone)‐block‐poly(p‐dioxanone) copolymers were prepared with varying feed rations by using two step polymerization reactions. Poly(trimethylenecarbonate)(ε‐caprolactone) random copolymer was synthesized with stannous‐2‐ethylhexanoate and followed by adding p‐dioxanone monomer as the other block. The ring opening polymerization was carried out at high temperature and long reaction time to get high molecular weight polymers. The monofilament fibers were obtained using conventional melting spun methods. The copolymers were identified by ¹H and ¹³C NMR spectroscopy and gel permeation chromatography (GPC). The physicochemical properties, such as viscosity, molecular weight, melting point, glass transition temperature, and crystallinity, were studied. The hydrolytic degradation of copolymers was studied in a phosphate buffer solution, pH = 7.2, 37 °C, and a biological absorbable test was performed in rats. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2790–2799, 2005     

Elaboration of densely functionalized polylactide nanoparticles from N‐acryloxysuccinimide‐based block copolymers

Poly(N‐acryloxysuccinimide) (PNAS) and poly(N‐acryloxysuccinimide‐co‐N‐vinylpyrrolidone) (P(NAS‐co‐NVP)) of adjustable molecular weights and narrow polydispersities were prepared by nitroxide‐mediated polymerization (NMP) in N,N‐dimethylformamide in the presence of free SG1 (N‐tert‐butyl‐N‐1‐diethylphosphono‐(2,2‐dimethylpropyl) nitroxide), with MAMA‐SG1 (N‐(2‐methylpropyl)‐N‐(1‐diethylphosphono‐2,2‐dimethylpropyl)‐O‐(2‐carboxylprop‐2‐yl)hydroxylamine) alkoxyamine as initiator. The reactivity ratios of NAS and NVP were determined to be r_NAS = 0.12 and r_NVP = 0, indicating a strong alternating tendency for the P(NAS‐co‐NVP) copolymer. NAS/NVP copolymerization was then performed from a SG1‐functionalized poly(D ,L ‐lactide) (PLA‐SG1) macro‐alkoxyamine as initiator, leading to the corresponding PLA‐b‐P(NAS‐co‐NVP) block copolymer, with similar NAS and NVP reactivity ratios as mentioned above. The copolymer was used as a surface modifier for the PLA diafiltration and nanoprecipitation processes to achieve nanoparticles in the range of 450 and 150 nm, respectively. The presence of the functional/hydrophilic P(NAS‐co‐NVP) block, and particularly the N‐succinimidyl (NS) ester moieties at the particle surface, was evidenced by ethanolamine derivatization and zeta potential measurements. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Thermosensitive behavior of poly(ethylene glycol)/poly(2‐(N,N‐dimethylamino)ethyl methacrylate) double hydrophilic block copolymers

The poly(ethylene glycol)/poly(2‐(N,N‐dimethylamino)ethyl methacrylate) (PEG/PDMAEMA) double hydrophilic block copolymers were synthesized by atom transfer radical polymerization using mPEG‐Br or Br‐PEG‐Br as macroinitiators. The narrow molecular weight distribution of PEG/PDMAEMA block copolymers was identified by gel permeation chromatography results. The thermosensitivity of PEG/PDMAEMA block copolymers in aqueous solution was revealed to depend significantly on pH, ionic strength, chain structure, and concentration of the block copolymers. By optimizing these factors, the cloud point temperature of PEG/PDMAEMA block copolymers can be limited within body temperature range (30–37 °C), which suggests that PEG/PDMAEMA block copolymers could be a good candidate for drug delivery systems. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 503–508, 2010     

Fully biodegradable polymeric micelles based on hydrophobic‐ and hydrophilic‐functionalized poly(lactide) block copolymers

Novel amphiphilic diblock copolymers from a combination of hydrophobic‐functional poly(lactides) (PLAs) with hydrophilic‐functional PLAs or poly(malic acid), respectively, toward fully biodegradable materials for medical applications, such as micellar drug delivery systems, are reported for the first time. The presented PLA‐based polymeric micelles are characterized by their small size below 100 nm, low critical micellar concentrations, good in vitro stabilities at room and body temperature, and efficient incorporation capability of hydrophobic compounds, particularly with regard to potential drug substances. Moreover, the advantage of being totally degradable with different rates at different pH values, as investigated in medical cancer treatment, is demonstrated. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3244–3254, 2010     

Amphiphilic block poly(propylene carbonate)‐block‐allyloxypolyethyleneglycol copolymer based shell cross‐linked micelles for controlled release of drug

Amphiphilic block poly(propylene carbonate)‐block‐allyloxypolyethyleneglycol (PPC‐b‐APEG) copolymer was synthesized by the click chemistry, and its structure were characterized. PPC‐b‐APEG can self‐assemble into micelles without emulsifier in water. Shell cross‐linked micelles were obtained by the reaction of the allyloxy groups, which were exposed on the outer of the PPC‐b‐APEG micelles, and N‐vinylpyrrolidone (NVP). The morphology and size of the micelles before and after cross‐link reactions were characterized. The research result shows that the shell cross‐linking could improve the stability of micelles. The particle size of uncross‐linked micelle was about 800 nm. The size of cross‐linked micelles increased with increasing amount of cross‐linking degree. To better evaluate the release behavior of PPC‐b‐PEG copolymer, doxorubicin (DOX)‐loaded micelles were synthesized using DOX as the model drug. Results showed that the DOX releasing rate decreased with increasing of NVP. The shell cross‐linking do decrease the burst release behaviours of DOX and reduce the DOX release rate.     

Synthesis and characterization of a series of biodegradable and biocompatible PEG‐supported poly(lactic‐ran‐glycolic acid) amphiphilic barbell‐like copolymers

A series of multihydroxyl (2, 4, and 8) terminated poly(ethylene glycol)s and their biodegradable, biocompatible, and branched barbell‐like (PLGA)_n‐b‐PEG‐b‐(PLGA)_n (n = 1, 2, 4) copolymers have been synthesized. The lengths of the PLGA arms were varied by controlling the molar ratio of monomers to hydroxyl groups of PEG ([LA+GA]₀/[? OH]₀ = 23, 45, 90). Chemical structures of synthesized barbell‐like copolymers were confirmed by both ¹H and ¹³C‐NMR spectroscopies. Molecular weights were determined by ¹H‐NMR end‐group analysis and gel permeation chromatography. The result of hydrolytic degradation indicated that the rate of degradation increased with the increase of arm numbers or with the decrease of arm lengths. The thermal properties were evaluated by using differential scanning calorimetry and a thermogravimetric analysis. The results indicated that the thermal properties of barbell‐like copolymers depended on the structural variations. The morphology of (PLGA)_n‐PEG‐(PLGA)_n copolymers self‐assembly films were investigated by atomic force microscope, the results indicated that the microphase separation existed in (PLGA)_n‐PEG‐(PLGA)_n copolymers. Because of the favorable biodegradability and biocompatibility of the PLGA and PEG, these results may therefore create new possibilities for these novel structural amphiphilic barbell‐like copolymers as potential biomaterials. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3802–3812, 2008     

pH‐ and temperature‐sensitive statistical copolymers poly[2‐(dimethylamino)ethyl methacrylate‐stat‐2‐vinylpyridine] with Functional succinimidyl‐ester chain ends synthesized by nitroxide‐mediated polymerization

Statistical copolymerizations of 2‐(dimethylamino)ethyl methacrylate (DMAEMA) with 2‐vinylpyridine (2VP) with 80 to 99 mol % DMAEMA in the feed utilizing a succinimidyl ester‐terminated alkoxyamine unimolecular initiator (NHS‐BlocBuilder) at 80 °C in bulk were performed. The effectiveness of 2VP as a controlling comonomer is demonstrated by linear increases in number‐average molecular weight versus conversion, relatively low PDI (1.5–1.6 with up to 98% DMAEMA) and successful chain extensions with 2VP. Additional free nitroxide does not significantly improve control for the DMAEMA/2VP copolymerizations. The succinimidyl ester on the initiator permits coupling to amine‐terminated poly(propylene glycol) (PPG), yielding an effective macroinitiator for synthesizing a doubly thermo‐responsive block copolymer of PPG‐block‐P(DMAEMA/2VP). A detailed study of the thermo‐ and pH‐sensitivities of the statistical and block copolymers is also presented. The cloud point temperature of the statistical copolymers is fine tuned from 14 to 75 °C by varying polymer composition and pH. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012.     

Controlled polymerization of 2‐(diethylamino)ethyl methacrylate and its block copolymer with N‐isopropylacrylamide by RAFT polymerization

Poly(2‐(diethylamino)ethyl methacrylate) (PDEAEMA) homopolymers with low polydispersities were synthesized by reversible addition fragmentation chain transfer (RAFT) radical polymerization. The performances of two chain transfer agents, 2‐cyanoprop‐2‐yl dithiobenzoate and 4‐cyanopentanic acid dithiobenzoate (CPADB), were compared. It was found that the polymerization of 2‐(diethylamino) ethyl methylacrylate was under good control in the presence of CPADB with 4,4′‐azobis(4‐cyanopentanoic acid) (ACPA) as initiator in 1,4‐dioxane at 70 °C. The kinetic behaviors were investigated under different CPADB/ACPA molar ratios. A long polymerization inhibition period was observed at high [CPADB]/[ACPA] ratio. The influences of [CPADB]/[ACPA] ratio, monomer/[CPADB] ratio, and temperature were studied with respect to monomer conversion, molecular weight control, and polydispersity index (PDI). The PDI decreased from 1.21 to 1.12, as the CPADB/ACPA molar ratio changed from 2 to 10. The molecular weight of PDEAEMA could be controlled by monomer/CPADB molar ratio. The control over MW and PDI was improved as the temperature increased from 60 to 70 °C; however, an additional increase to 80 °C led to a loss of control. Using PDEAEMA macroRAFT agent, pH/thermo double‐responsive block copolymers of PDEAEMA and poly(N‐isopropylacrylamide) (PDEAEMA‐b‐PNIPAM) with narrow polydispersity (PDI, 1.24) were synthesized. The lower critical solution temperature of PDEAEMA‐b‐PNIPAM block copolymer depended on the environmental pH. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3294–3305, 2008     

A novel route for preparation of multifunctional polymeric nanocarriers for stimuli‐triggered drug release

Fluorescence‐incorporated, crosslinker‐free, pH‐ and thermoresponsive nanocarriers were prepared by the incorporation of drug molecules into the thermoresponsive nanocapsules, which composed of poly(N‐isopropylacrylamide) (PNIPAAm) with carboxylic acid end groups via temperature induced self‐assembling method. Well‐defined, pH‐responsive carboxylic acid group‐ended PNIPAAm homopolymer (HOOC? PNIPAAm? COOH) was synthesized by reversible addition fragmentation chain transfer polymerization with S,S′‐bis(α,α′‐dimethyl‐α″‐acetic acid)trithiocarbonate (CMP) as a chain transfer agent. Rhodamine 6G (R6G), the model drug, was used for three kinds of application: First, the nanostructure fixing; second, the fluorescence‐labeling; and last, the controlled release modeling. The transmission electron microscope images showed the solution type dosing led to the encapsulation of drug molecules into the nanocarriers, while the powder‐type drug‐loading process significantly contributed to the structure preservation of nanocarriers. The controlled release behaviors with various pH values and temperatures were evaluated. These multifunctional nanocarriers have potential to be applied for the biomedical therapy by stimuli‐responsive controlled release. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 561–571     

Synthesis and morphology of all‐conjugated donor–acceptor block copolymers based on poly(3‐hexylthiophene) and poly(naphthalene diimide)

A series of all‐conjugated diblock and triblock copolymers comprised of poly(naphthalene diimide) (PNDI)‐based n‐type and the poly(3‐hexylthiophene) (P3HT) segments could be synthesized via the Kumada catalyst‐transfer polycondensation process. The crystalline structures and chain orientation of the block copolymer thin films were systematically studied by grazing incident wide‐angle X‐ray scattering (GIWAXS). The GIWAXS results indicated that both the P3HT and PNDI segments in the block copolymers form exclusive crystalline domains in which the P3HT domain aligns with an edge‐on rich orientation, and the PNDI domain aligns with a face‐on rich orientation. In contrast, the blend films of the P3HT and PNDI homopolymers also show two distinguished crystalline domains in which the P3HT domain aligns with an edge‐on rich orientation, and the PNDI domains align in different ways depending on the chemical structure of n‐type polymers, that is, PNDI1Th is isotropically dispersed, while PNDI2Th aligns with a face‐on rich orientation. In addition, the effect of thermal annealing on the crystalline behavior of the block copolymers is reported. The GIWAXS results indicated that thermal annealing increases the crystallinity of both segments without affecting their chain orientation. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1139–1148     

Dual‐responsive supramolecular inclusion complexes of block copolymer poly(ethylene glycol)‐block‐poly[(2‐dimethylamino)ethyl methacrylate] with α‐cyclodextrin

A new class of temperature and pH dual‐responsive and injectable supramolecular hydrogel was developed, which was formed from block copolymer poly(ethylene glycol)‐block‐poly[(2‐dimethylamino)ethyl methacrylate] (PEG‐b‐PDMAEMA) and α‐cyclodextrin (α‐CD) inclusion complexes (ICs). The PEG‐b‐PDMAEMA diblock copolymers with different ratio of ethylene glycol (EG) to (2‐dimethylamino)ethyl methacrylate (DMAEMA) (102:46 and 102:96, respectively) were prepared by atom transfer radical polymerization (ATRP). ¹H NMR measurement indicated that the ratio of EG unit to α‐CD in the resulted ICs was higher than 2:1. Thermal analysis showed that thermal stability of ICs was improved. The rheology studies showed that the hydrogels were temperature and pH sensitive. Moreover, the hydrogels were thixotropic and reversible. The self‐assembly morphologies of the ICs in different pH and ionic strength environment were studied by transmission electron microscopy. The formed biocompatible micelles have potential applications as biomedical and stimulus‐responsive material. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2143–2153, 2010     

Thermosensitive t‐PLA‐b‐PNIPAAm tri‐armed star block copolymer nanoscale micelles for camptothecin drug release

Thermosensitive polylactide‐block‐poly(N‐isopropylacrylamide) (t‐PLA‐b‐PNIPAAm) tri‐armed star block copolymers were synthesized by atom transfer radical polymerization (ATRP) of monomer NIPAAm using t‐PLA‐Cl as macroinitiator. The synthesis of t‐PLA‐Cl was accomplished by esterification of star polylactides (t‐PLA) with 2‐chloropropionyl chloride using trimethylolpropane as a center molecule. FT‐IR, ¹H NMR, and GPC analyses confirmed that the t‐PLA‐b‐PNIPAAm star block copolymers had well‐defined structure and controlled molecular weights. The block copolymers could form core‐shell micelle nanoparticles due to their hydrophilic‐hydrophobic trait in aqueous media, and the critical micelle concentrations (CMC) were from 6.7 to 32.9 mg L^?1, depending on the system composition. The as‐prepared micelle nanoparticles showed reversible phase changes in transmittance with temperature: transparent below low critical solution temperature (LCST) and opaque above the LCST. Transmission electron microscopy (TEM) observations revealed that the micelle nanoparticles were spherical in shape with core‐shell structure. The hydrodynamic diameters of the micelle nanoparticles depended on copolymer compositions, micelle concentrations and media. MTT assays were conducted to evaluate cytotoxicity of the camptothecin‐loaded copolymer micelles. Camptothecin drug release studies showed that the copolymer micelles exhibited thermo‐triggered targeting drug release behavior, and thus had potential application values in drug controlled delivery. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4429–4439