Synthesis of inositol‐based star polymers through low ppm ATRP methods

The vitamin B₈‐based macroinitiator with six 2‐bromoisobutyric initiating sites was prepared for the first time by the transesterification reaction of meso‐inositol with 2‐bromoisobutyryl bromide. A series of six‐armed (co)polymers, containing hydrophilic poly(di(ethylene glycol) methyl ether methacrylate) and amphiphilic poly(di(ethylene glycol) methyl ether methacrylate)‐block‐poly(methyl methacrylate) as the arms and meso‐inositol as the core, were obtained by low ppm atom transfer radical polymerization (ATRP) methods, utilizing 30 ppm of catalyst complex. Under Fe⁰‐mediated supplemental activators and reducing agents ATRP, Cu⁰‐mediated supplemental activators and reducing agents ATRP, Ag⁰‐mediated activators regenerated by electron transfer ATRP, and simplified electrochemically mediated ATRP conditions, polymerization proceeded on to high conversion while maintaining low dispersity (?  = 1.05–1.16) giving well‐defined six‐armed star (co)polymers. ¹H NMR spectral results confirm the formation of new star‐shaped block (co)polymers. The absence of intermolecular coupling reactions during synthesis was confirmed by gel permeation chromatography analyses of the side chains of received star (co)polymers. These vitamin B₈‐based star (co)polymers may find biomedical applications as thermo‐sensitive drug delivery systems, biosensors, and tissue engineering solutions. Copyright © 2017 John Wiley & Sons, Ltd.     

A New Approach for the Synthesis of Miktoarm Star Polymers Through a Combination of Thiol–Epoxy “Click” Chemistry and ATRP/Ring‐Opening Polymerization Techniques

A new approach was developed for synthesis of certain A₃B₃‐type of double hydrophilic or amphiphilic miktoarm star polymers using a combination of “grafting onto” and “grafting from” methods. To achieve the synthesis of desired miktoarm star polymers, acetyl protected poly(ethylene glycol) (PEG) thiols (M_n = 550 and 2000 g mol^?1) were utilized to generate A₃‐type of homoarm star polymers through an in situ protective group removal and a subsequent thiol–epoxy “click” reaction with a tris‐epoxide core viz. 1,1,1‐tris(4‐hydroxyphenyl)ethane triglycidyl ether. The secondary hydroxyl groups generated adjacent to the core upon the thiol–epoxy reaction were esterified with α‐bromoisobutyryl bromide to install atom transfer radical polymerization (ATRP) initiating sites. ATRP of N‐isopropylacrylamide (NIPAM) using the three‐arm star PEG polymer fitted with ATRP initiating sites adjacent to the core afforded A₃B₃‐type of double hydrophilic (PEG)₃[poly(N‐isopropylacrylamide)] (PNIPAM)₃ miktoarm star polymers. Furthermore, the generated hydroxyl groups were directly used as initiator for ring‐opening polymerization of ε‐caprolactone to prepare A₃B₃‐type of amphiphilic (PEG)₃[poly(ε‐caprolactone)]₃ miktoarm star polymers. The double hydrophilic (PEG)₃(PNIPAM)₃ miktoarm star polymers showed lower critical solution temperature around 34 °C. The preliminary transmission electron microscopy analysis indicated formation of self‐assembly of (PEG)₃(PNIPAM)₃ miktoarm star polymer in aqueous solution. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 146–156     

Self‐assembly of amphiphilic tris(2,2′‐bipyridine)ruthenium‐cored star‐shaped polymers

Amphiphilic tris(2,2′‐bipyridine)ruthenium‐cored star‐shaped polymers consisting of one polystyrene block and two poly(N‐isopropylacrylamide) blocks were prepared by the “arm‐first” method in which RAFT polymerization and nonconvalent ligand–metal complexation were employed. The prepared amphiphilic star‐shaped metallopolymers are able to form micelles in water. The size and distribution of the micelles were studied by dynamic light scattering and transmission electron microscopy techniques. Preliminary studies indicate that the polymer concentration and the hydrophilic poly(N‐isopropylacrylamide) block length can affect the morphologies of the formed metal‐interfaced core–shell micelles in water. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4204–4210, 2007     

Disulfide‐centered star‐shaped polypeptide‐PEO block copolymers for reduction‐triggered drug release

Disulfide‐centered star‐shaped poly(ε‐benzyloxycarbonyl‐l ‐lysine)‐b‐poly(ethylene oxide) block copolymers (i.e., A₂B₄ type Cy‐PZlys‐b‐PEO) were synthesized by the combination of ring‐opening polymerization and thiol‐yne chemistry. Their molecular structures and physical properties were characterized in detail by FTIR, ¹H NMR, gel permeation chromatography, differential scanning calorimetry, wide‐angle X‐ray diffraction, and polarized optical microscope. Despite mainly exhibiting an α‐helix conformation, the inner PZlys blocks within copolymers greatly prohibited the crystallinity of the outer PEO blocks and presented a liquid crystal phase transition behavior in solid state. These block copolymers Cy‐PZlys‐b‐PEO self‐assembled into nearly spherical micelles in aqueous solution, which had a hydrophobic disulfide‐centered PZlys core surrounded by a hydrophilic PEO corona. As monitored by means of DLS and TEM, these micelles were progressively reduced to smaller micelles in 10 mM 1,4‐dithiothreitol at 37 °C and finally became ones with a half size, demonstrating a reduction‐sensitivity. Despite a good drug‐loading property, the DOX‐loaded micelles of Cy‐PZlys‐b‐PEO exhibited a reduction‐triggered drug release profile with an improved burst‐release behavior compared with the linear counterpart. Importantly, this work provides a versatile strategy for the synthesis of the disulfide‐centered star‐shaped polypeptide block copolymers potential for intracellular glutathione‐triggered drug delivery systems. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2000–2010     

Star‐shaped cyclopolymers: A new category of star polymer with rigid cyclized arms prepared by controlled cationic cyclopolymerization and subsequent microgel formation of divinyl ethers

The combination of living/controlled cationic cyclopolymerization and crosslinking polymerization of bifunctional vinyl ethers (divinyl ethers) was applied to the synthesis of core‐crosslinked star‐shaped polymers with rigid cyclized arms. Cyclopolymerization of 4,4‐bis(vinyloxymethyl)cyclohexene ( 1 ), a divinyl ether with a cyclohexene group, was investigated with the hydrogen chloride/zinc chloride (HCl/ZnCl₂) initiating system in toluene at 0 °C. The reaction proceeded quantitatively to give soluble poly( 1 )s in organic solvents. The content of the unreacted vinyl groups in the produced polymers was less than ～3 mol%, and therefore, the degree of cyclization of the polymers was determined to be ～97%. The number‐average molecular weight (M_n) of the polymers increased in direct proportion to monomer conversion and further increased on addition of a fresh monomer feed to the almost completely polymerized reaction mixture, indicating that living cyclopolymerization of 1 occurred. The chain linking reactions among the formed living cyclopolymers with 1,4‐bis(vinyloxy)cyclohexane ( 3 ) as a crosslinker in toluene at 0 °C produced core‐crosslinked star‐shaped cyclopoly( 1 )s [star‐poly( 1 )s] in high yield (100%). Dihydroxylation of the cyclohexene double bonds of star‐poly( 1 ) gave hydrophilic water‐soluble star‐shaped polymers with rigid arm structure [star‐poly( 1 )‐OH] with thermo‐responsive function in water. T_gs of star‐poly( 1 ) and star‐poly( 1 )‐OH were 135 °C and 216 °C, respectively; these values are very high as vinyl ether‐based star‐shaped polymers. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1094–1102     

Encapsulation and release by star‐shaped block copolymers as unimolecular nanocontainers

A five‐arm star‐shaped poly(ethylene oxide) (PEO) with terminal bromide groups was used as a macroinitiator for the atom transfer radical polymerization of tert‐butyl acrylate (tBA), resulting in five‐arm star‐shaped poly(ethylene oxide)‐block‐poly(tert‐butyl acrylate) block copolymers. The polymerization proceeded in a controlled way using a copper(I)bromide/pentamethyl diethylenetriamine catalytic system in acetonitrile as solvent. The hydrolysis of the tBA blocks of the amphiphilic star‐shaped PEO‐b‐PtBA block copolymer resulted in dihydrophilic star structures. The encapsulation of the star‐block copolymers and their release properties in acid environment have been followed by UV‐spectroscopy and color changes, using the dye methyl orange as a hydrophilic guest molecule. Characterization of the structures has been done by ¹H NMR, size exclusion chromatography, MALDI‐TOF, and differential scanning calorimetry. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 650–660, 2008     

Synthesis of fluorine‐containing star‐shaped poly(vinyl ether)s via arm‐linking reactions in living cationic polymerization

Various types of fluorine‐containing star‐shaped poly(vinyl ether)s were successfully synthesized by crosslinking reactions of living polymers based on living cationic polymerization. Star polymers with fluorinated arm chains were prepared by the reaction between a divinyl ether and living poly(vinyl ether)s with fluorine groups (C₄F₉, C₆F₁₃, and C₈F₁₇) at the side chain using cationogen/Et_1.5AlCl_1.5 in a fluorinated solvent (dichloropentafluoropropanes), giving star‐shaped fluorinated polymers in high yields with a relatively narrow molecular weight distribution. The concentration of living polymers for the crosslinking reaction and the molar feed ratio of a bifunctional vinyl ether to living polymers affected the yield and molecular weight of the star polymers. Star polymers with block arms were prepared by a linking reaction of living block copolymers of a fluorinated segment and a nonfluorinated segment. Heteroarm star‐shaped polymers containing two‐ or three‐arm species were synthesized using a mixture of different living polymer species for the reaction with a bifunctional vinyl ether. The obtained polymers underwent temperature‐induced solubility transitions in various organic solvents, and their concentrated solutions underwent sol–gel transitions, based on the solubility transition of a thermoresponsive fluorinated segment. Furthermore, a slight amount of fluorine groups were shown to be effective for physical gelation when those were located at the arm ends of a star polymer. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Microwave‐assisted synthesis of star‐shaped poly(ε‐caprolactone)‐block‐poly(L‐lactide) copolymers and the crystalline morphologies

A monomode microwave reactor was used for the synthesis of designed star‐shaped polymers, which were based on dipentaerythritol with six crystallizable arms of poly(ε‐caprolactone)‐b‐poly(L ‐lactide) (PCL‐b‐PLLA) copolymer via a two‐step ring‐opening polymerization (ROP). The effects of irradiation conditions on the molecular weight were studied. Microwave heating accelerated the ROP of CL and LLA, compared with the conventional heating method. The resultant hexa‐armed polymers were fully characterized by means of FTIR, ¹H NMR spectrum, and GPC. The investigation of thermal properties and crystalline behaviors indicated that the crystalline behaviors of polymers were largely depended on the macromolecular architecture and the length of the block chains. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Synthesis of well‐defined cyclodextrin‐core star polymers

The synthesis of 21‐arm methyl methacrylate (MMA) and styrene star polymers is reported. The copper (I)‐mediated living radical polymerization of MMA was carried out with a cyclodextrin‐core‐based initiator with 21 independent discrete initiation sites: heptakis[2,3,6‐tri‐O‐(2‐bromo‐2‐methylpropionyl]‐β‐cyclodextrin. Living polymerization occurred, providing well‐defined 21‐arm star polymers with predicted molecular weights calculated from the initiator concentration and the consumed monomer as well as low polydispersities [e.g., poly(methyl methacrylate) (PMMA), number‐average molecular weight (M_n) = 55,700, polydispersity index (PDI) = 1.07; M_n = 118,000, PDI = 1.06; polystyrene, M_n = 37,100, PDI = 1.15]. Functional methacrylate monomers containing poly(ethylene glycol), a glucose residue, and a tert‐amine group in the side chain were also polymerized in a similar fashion, leading to hydrophilic star polymers, again with good control over the molecular weight and polydispersity (M_n = 15,000, PDI = 1.03; M_n = 36,500, PDI = 1.14; and M_n = 139,000, PDI = 1.09, respectively). When styrene was used as the monomer, it was difficult to obtain well‐defined polystyrene stars at high molecular weights. This was due to the increased occurrence of side reactions such as star–star coupling and thermal (spontaneous) polymerization; however, low‐polydispersity polymers were achieved at relatively low conversions. Furthermore, a star block copolymer consisting of PMMA and poly(butyl methacrylate) was successfully synthesized with a star PMMA as a macroinitiator (M_n = 104,000, PDI = 1.05). © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2206–2214, 2001     

Hyperbranched polymers as scaffolds for multifunctional reversible addition–fragmentation chain‐transfer agents: A route to polystyrene‐core‐polyesters and polystyrene‐block‐poly(butyl acrylate)‐core‐polyesters

Polydisperse hyperbranched polyesters were modified for use as novel multifunctional reversible addition–fragmentation chain‐transfer (RAFT) agents. The polyester‐core‐based RAFT agents were subsequently employed to synthesize star polymers of n‐butyl acrylate and styrene with low polydispersity (polydispersity index < 1.3) in a living free‐radical process. Although the polyester‐core‐based RAFT agent mediated polymerization of n‐butyl acrylate displayed a linear evolution of the number‐average molecular weight (M_n) up to high monomer conversions (>70%) and molecular weights [M_n > 140,000 g mol^?1, linear poly(methyl methacrylate) equivalents)], the corresponding styrene‐based system reached a maximum molecular weight at low conversions (≈30%, M_n = 45,500 g mol^?1, linear polystyrene equivalents). The resulting star polymers were subsequently used as platforms for the preparation of star block copolymers of styrene and n‐butyl acrylate with a polyester core with low polydispersities (polydispersity index < 1.25). The generated polystyrene‐based star polymers were successfully cast into highly regular honeycomb‐structured microarrays. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3847–3861, 2003     

Multiarm star block copolymers via Diels‐Alder click reaction

Two types of multiarm star block copolymers: (polystyrene)_m‐poly(divinylbenzene)‐poly(methyl methacrylate)_n, (PS)_m‐polyDVB‐(PMMA)_n and (polystyrene)_m‐poly(divinylbenzene)‐poly(tert‐butyl acrylate)_k, (PS)_m‐polyDVB‐(PtBA)_k were successfully prepared via a combination of cross‐linking and Diels–Alder click reactions based on “arm‐first” methodology. For this purpose, multiarm star polymer with anthracene functionality as reactive periphery groups was prepared by a cross‐linking reaction of divinyl benzene using α‐anthracene end functionalized polystyrene (PS‐Anth) as a macroinitiator. Thus, obtained multiarm star polymer was then reacted with furan protected maleimide‐end functionalized polymers: PMMA‐MI or PtBA‐MI at reflux temperature of toluene for 48 h resulting in the corresponding multiarm star block copolymers via Diels–Alder click reaction. The multiarm star and multiarm star block copolymers were characterized by using ¹H NMR, SEC, Viscotek triple detection SEC (TD‐SEC) and UV. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 178–187, 2009     

Synthesis of star‐shaped poly(D,L‐lactic acid‐alt‐glycolic acid)‐b‐poly(L‐lactic acid) with the poly(D,L‐lactic acid‐alt‐glycolic acid) macroinitiator and stannous octoate catalyst

Two types of three‐arm and four‐arm, star‐shaped poly(D,L ‐lactic acid‐alt‐glycolic acid)‐b‐poly(L ‐lactic acid) (D,L ‐PLGA50‐b‐PLLA) were successfully synthesized via the sequential ring‐opening polymerization of D,L ‐3‐methylglycolide (MG) and L ‐lactide (L ‐LA) with a multifunctional initiator, such as trimethylolpropane and pentaerythritol, and stannous octoate (SnOct₂) as a catalyst. Star‐shaped, hydroxy‐terminated poly(D,L ‐lactic acid‐alt‐glycolic acid) (D,L ‐PLGA50) obtained from the polymerization of MG was used as a macroinitiator to initiate the block polymerization of L ‐LA with the SnOct₂ catalyst in bulk at 130 °C. For the polymerization of L ‐LA with the three‐arm, star‐shaped D,L ‐PLGA50 macroinitiator (number‐average molecular weight = 6800) and the SnOct₂ catalyst, the molecular weight of the resulting D,L ‐PLGA50‐b‐PLLA polymer linearly increased from 12,600 to 27,400 with the increasing molar ratio (1:1 to 3:1) of L ‐LA to MG, and the molecular weight distribution was rather narrow (weight‐average molecular weight/number‐average molecular weight = 1.09–1.15). The ¹H NMR spectrum of the D,L ‐PLGA50‐b‐PLLA block copolymer showed that the molecular weight and unit composition of the block copolymer were controlled by the molar ratio of L ‐LA to the macroinitiator. The ¹³C NMR spectrum of the block copolymer clearly showed its diblock structures, that is, D,L ‐PLGA50 as the first block and poly(L ‐lactic acid) as the second block. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 409–415, 2002     

Synthesis of amphiphilic A4B4 star‐shaped copolymers by mechanisms transformation combining with thiol‐ene reaction

Using core‐first strategy, the amphiphilic A₄B₄ star‐shaped copolymers [poly(ethylene oxide)]₄[poly(ε‐caprolactone)]₄ [(PEO)₄(PCL)₄], [poly(ethylene oxide)]₄[poly(styrene)]₄ [(PEO)₄(PS)₄], and [poly(ethylene oxide)]₄[poly(tert‐butyl acrylate)]₄ [(PEO)₄(PtBA)₄] were synthesized by mechanisms transformation combining with thiol‐ene reaction. First, using a designed multifunctional mikto‐initiator with four active hydroxyl groups and four allyl groups, the four‐armed star‐shaped polymers (PEO‐Ph)₄/(OH)₄ with four active hydroxyl groups at core position were obtained by sequential ring‐opening polymerization (ROP) of ethylene oxide monomers, capping reaction of living oxyanion with benzyl chloride, and transformation of allyl groups into hydroxyl groups by thiol‐ene reaction. Then, the A₄B₄ star‐shaped copolymers (PEO)₄(PS)₄ or (PEO)₄(PtBA)₄ were obtained by atom transfer radical polymerization (ATRP) of styrene or tert‐butyl acrylate (tBA) monomers from macroinitiator of (PEO‐Ph)₄/(Br)₄, which was obtained by esterification of (PEO‐Ph)₄/(OH)₄ with 2‐bromoisobutyryl bromide. The A₄B₄ star‐shaped copolymers (PEO)₄(PCL)₄ were also obtained by ROP of ε‐caprolactopne monomers from macroinitiator of (PEO‐Ph)₄/(OH)₄. The target copolymers and intermediates were characterized by size‐exclusion chromatography, matrix‐assisted laser desorption/ionization time‐of‐flight mass spectroscopy, and nuclear magnetic resonance in detail. This synthetic route might be a versatile one to various A_nB_n (n ≥ 3) star‐shaped copolymers with defined structure and compositions. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4572–4583     

Synthesis,characterization, and thermal properties of a novel pentaerythritol‐initiated star‐shaped poly(p‐dioxanone)

A novel star‐shaped poly(p‐dioxanone) was synthesized by the ring‐opening polymerization of p‐dioxanone initiated by pentaerythritol with stannous octoate as a catalyst in bulk. The effect of the molar ratio of the monomer to the initiator on the polymerization was studied. The polymers were characterized with ¹H NMR and ¹³C NMR spectroscopy. The thermal properties of the polymers were investigated with differential scanning calorimetry and thermogravimetric analysis. The novel star‐shaped poly(p‐dioxanone) has a potential use in biomedical materials. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1245–1251, 2006     

Synthesis of well‐defined star‐shaped poly(ε‐caprolactone)/poly(ethylbene glycol) amphiphilic conetworks by combination of ring opening polymerization and “click” chemistry

Well‐defined star‐shaped hydrophobic poly(ε‐caprolactone) (PCL) and hydrophilic poly(ethylene glycol) (PEG) amphiphilic conetworks (APCNs) have been synthesized via the combination of ring opening polymerization (ROP) and click chemistry. Alkyne‐terminated six arm star‐shaped PCL (6‐s‐PCLx‐C?CH) and azido‐terminated PEG (N₃‐PEG‐N₃) are characterized by ¹H NMR and FT‐IR. The swelling degree of the APCNs is determined both in water and organic solvent. This unique property of the conetworks is dependent on the nanophase separation of hydrophilic and hydrophobic phases. The morphology and thermal behaviors of the APCNs are investigated by SEM and DSC respectively. The biocompatibility is determined by water soluble tetrazolium salt reagents (WST‐1) assay, which shows the new polymer networks had good biocompatibility. Through in vitro release of paclitaxel (PTX) and doxorubicin (DOX), the APCNs is confirmed to be promising drug depot materials for sustained hydrophobic and hydrophilic drugs. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 407–417     

Controlled synthesis of pH‐responsive amphiphilic A2B2 miktoarm star block copolymer by combination of SET‐LRP and RAFT polymerization

The pH‐responsive amphiphilic A₂B₂ miktoarm star block copolymer, poly(acrylic acid)₂‐poly(vinyl acetate)₂ [(PAA)₂(PVAc)₂], with controlled molecular weight and well‐defined structure was successfully synthesized via combination of single‐electron transfer‐mediated living radical polymerization (SET‐LRP) and reversible addition‐fragmentation chain transfer (RAFT) polymerization methods. First, the precursor two‐armed poly(t‐butyl acrylate) (PtBA)₂ functionalized with two xanthate groups was prepared by SET‐LRP of t‐butyl acrylate in acetone at 25 °C using the novel tetrafunctional bromoxanthate (Xanthate₂‐Br₂) as an Iniferter (initiator‐transfer agent‐terminator) agent. The polymerization behavior showed typical LRP natures by the first‐order polymerization kinetics and the linear dependence of molecular weight of the polymer on the monomer conversion. Second, the A₂B₂ miktoarm star block copolymer (PtBA)₂(PVAc)₂ was prepared by RAFT polymerization of VAc using (PtBA‐N₃)₂(Xanthate)₂ obtained as the macro‐RAFT agent. Finally, the pH‐sensitive A₂B₂ amphiphilic miktoarm star block copolymer poly(acrylic acid)₂‐poly(vinyl acetate)₂ ((PAA)₂(PVAc)₂) was obtained by selectively cleavage of t‐butyl esters of (PtBA)₂(PVAc)₂. All the miktoarm star block copolymers were characterized by GPC, ¹H‐NMR, and FT‐IR spectra. The self‐assembly behaviors of the amphiphilic A₂B₂ miktoarm block copolymers (PAA)₂(PVAc)₂ were also investigated by transmission electron microscopy. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2009     

Novel synthesis of biodegradable amphiphilic linear and star block copolymers based on poly(ε‐caprolactone) and poly(ethylene glycol)

Biodegradable, amphiphilic, diblock poly(ε‐caprolactone)‐block‐poly(ethylene glycol) (PCL‐b‐PEG), triblock poly(ε‐caprolactone)‐block‐poly(ethylene glycol)‐block‐poly(ε‐caprolactone) (PCL‐b‐PEG‐b‐PCL), and star shaped copolymers were synthesized by ring opening polymerization of ε‐caprolactone in the presence of poly(ethylene glycol) methyl ether or poly(ethylene glycol) or star poly(ethylene glycol) and potassium hexamethyldisilazide as a catalyst. Polymerizations were carried out in toluene at room temperature to yield monomodal polymers of controlled molecular weight. The chemical structure of the copolymers was investigated by ¹H and ¹³C NMR. The formation of block copolymers was confirmed by ¹³C NMR and DSC investigations. The effects of copolymer composition and molecular structure on the physical properties were investigated by GPC and DSC. For the same PCL chain length, the materials obtained in the case of linear copolymers are viscous whereas in the case of star copolymer solid materials are obtained with low T_g and T_m temperatures. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3975–3985, 2007     

Synthesis,self‐assembly and recognition properties of biomimetic star‐shaped poly(ε‐caprolactone)‐b‐glycopolymer block copolymers

Biomimetic star‐shaped poly(ε‐caprolactone)‐b‐poly(gluconamidoethyl methacrylate) block copolymers (SPCL‐PGAMA) were synthesized from the atom transfer radical polymerization (ATRP) of unprotected GAMA glycomonomer using a tetra(2‐bromo‐2‐methylpropionyl)‐terminated star‐shaped poly(ε‐caprolactone) (SPCL‐Br) as a macroinitiator in NMP solution at room temperature. The block length of PGAMA glycopolymer within as‐synthesized SPCL‐PGAMA copolymers could be adjusted linearly by controlling the molar ratio of GAMA glycomonomer to SPCL‐Br macroinitiator, and the molecular weight distribution was reasonably narrow. The degree of crystallization of PCL block within copolymers decreased with the increasing block length ratio of outer PGAMA to inner PCL. Moreover, the self‐assembly properties of the SPCL‐PGAMA copolymers were investigated by NMR, UV‐vis, DLS, and TEM, respectively. The self‐assembled glucose‐installed aggregates changed from spherical micelles to worm‐like aggregates, then to vesicles with the decreasing weight fraction of hydrophilic PGAMA block. Furthermore, the biomolecular binding of SPCL‐PGAMA with Concanavalin A (Con A) was studied by means of UV‐vis, fluorescence spectroscopy, and DLS, which demonstrated that these SPCL‐PGAMA copolymers had specific recognition with Con A. Consequently, this will not only provide biomimetic star‐shaped SPCL‐PGAMA block copolymers for targeted drug delivery, but also improve the compatibility and drug release properties of PCL‐based biomaterials for hydrophilic peptide drugs. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 817–829, 2008     

Synthesis and characterization of pH sensitive poly(glycidol)‐b‐poly(4‐vinylpyridine) block copolymers

Block copolymers of poly(glycidol)‐b‐poly(4‐vinylpyridine) were obtained by ATRP of 4‐vinylpyridine initiated by ω‐(2‐chloropropionyl) poly(glycidol) macroinitiators. By changing the monomer/macroinitiator ratio in the synthesis polymers with varied P4VP/PGl molar ratio were obtained. The obtained block copolymers showed pH sensitive solubility. It was found that the linkage of a hydrophilic poly(glycidol) block to a P4VP influenced the pK_a value of P4VP. DLS measurements showed the formation of fully collapsed aggregates exceeding pH 4.7. Above this pH values the collapsed P4VP core of the aggregates was stabilized by a surrounding hydrophilic poly(glycidol) corona. The size of the aggregates depended significantly upon the composition of the block copolymers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1782–1794, 2009     

Synthesis and Characterization of New Block Copolymers with Poly(ethylene oxide) and Poly[3(S)‐sec‐butylmorpholine‐2,5‐dione] Sequences

Four different types of polydepsipeptide‐polyether block copolymers were synthesized via ring‐opening polymerization of 3(S)‐sec‐butylmorpholine‐2,5‐dione (BMD) in the presence of hydroxytelechelic poly(ethylene oxide) (PEO) with stannous octoate as a catalyst.The polymers were an AB block copolymer, an ABA block copolymer, an (A)₂B star shaped copolymer and an (A)₂B(A)₂ copolymer, where A is a poly[3(S)‐sec‐butylmorpholine‐2,5‐dione] (PBMD) and B a poly(ethylene oxide) block. The molar ratio of BMD to PEO was varied to obtain copolymers with different weight fractions of PBMD blocks ranging from 59.8 to 96.7 wt.‐%. The crystallinity of the PEO phase in the copolymers decreases in the following order: AB > (A)₂B > ABA > (A)₂B(A)₂ . The static contact angle θ decreases with increasing PEO content in the block copolymers.