Microphase separation behavior on the surfaces of poly(dimethylsiloxane)‐block‐poly(2,2,3,3,4,4,4‐heptafluorobutyl methacrylate) diblock copolymer coatings

Microphase separation behavior on the surfaces of poly(dimethylsiloxane)‐block‐poly(2,2,3,3,4,4,4‐heptafluorobutyl methacrylate) (PDMS‐b‐PHFBMA) diblock copolymer coatings was investigated. The PDMS‐b‐PHFBMA diblock copolymers were successfully synthesized via atom transfer radical polymerization (ATRP). The chemical structure of the copolymers was characterized by nuclear magnetic resonance and Fourier transform infrared spectroscopy. Surface composition was studied by X‐ray photoelectron spectroscopy. Copolymer microstructure was investigated by atomic force microscopy. The microstructure observations show that well‐organized phase‐separated surfaces consist of hydrophobic domain from PDMS segments and more hydrophobic domain from PHFBMA segments in the copolymers. The increase in the PHFBMA content can strengthen the microphase separation behavior in the PDMS‐b‐PHFBMA diblock copolymers. And the increase in the annealing temperature can also strengthen the microphase separation behavior in the PDMS‐b‐PHFBMA diblock copolymers. Moreover, Flory‐Huggins thermodynamic theory was preliminarily used to explain the microphase separation behavior in the PDMS‐b‐PHFBMA diblock copolymers.© 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Poly(dimethylsiloxane‐b‐styrene) diblock copolymers prepared by reversible addition–fragmentation chain‐transfer polymerization: Synthesis and characterization

Well‐defined poly(dimethylsiloxane‐b‐styrene) diblock copolymers were prepared by reversible addition–fragmentation chain‐transfer (RAFT) polymerization. Monohydroxyl‐terminated polydimethylsiloxane was modified to form a functional polydimethylsiloxane/macro‐RAFT agent, which was reacted with styrene to form the diblock copolymers. The chemical compositions and structures of the copolymers were characterized by proton nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, and gel permeation chromatography. The surface properties and morphology of the copolymers were investigated with static water contact‐angle measurements, X‐ray photoelectron spectroscopy, transmission electron microscopy, and atomic force microscopy, which showed a low surface energy and microphase separation surfaces that were composed of hydrophobic domains from polydimethylsiloxane segments. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis of poly(fluorinated styrene)‐block‐poly(ethylene oxide) amphiphilic copolymers via atom transfer radical polymerization: potential application as paper coating materials

BACKGROUND: The surface of a substrate which comprises a fibrous material is brought into contact with a type of amphiphilic block copolymer which comprises hydrophilic/hydrophobic polymeric blocks. These amphiphilic copolymers have been synthesized by atom transfer radical polymerization (ATRP) technique. The atom transfer radical polymerization of poly(2,3,4,5,6‐pentafluorostyrene)‐block‐poly(ethylene oxide) (PFS‐b‐PEO) copolymers (di‐ and triblock structures) with various ranges of PEO molecular weights was initiated by a PEO chloro‐telechelic macroinitiator. The polymerization, carried out in bulk and catalysed by copper(I) chloride in the presence of 2,2′‐bipyridine ligand, led to A–B–A amphiphilic triblock and A–B amphiphilic diblock structures. RESULTS: With most of the macroinitiators, the living nature of the polymerizations led to block copolymers with narrow molecular weight distributions (1.09 < M_w/M_n < 1.33) and well‐controlled molecular structures. These block copolymers turned out to be water‐soluble through adjustment of the PEO block content (>90 wt%). Of all the block copolymers synthesized, PFS‐b‐PEO(10k)‐b‐PFS containing 10 wt% PFS was found to retard water absorption considerably. CONCLUSION: The printability of paper treated with the copolymers was evaluated with contact angle measurements and felt pen tests. The adsorption of such copolymers at the solid/liquid interface is relevant to the wetting and spreading of liquids on hydrophobic/hydrophilic surfaces. Copyright © 2009 Society of Chemical Industry     

Preparation of diblock copolymers consisting of methoxy poly(ethylene glycol) and poly(ε‐caprolactone)/poly(L‐lactide) and their degradation property

Methoxy poly(ethylene glycol)‐b‐poly(ε‐caprolactone) (MPEG‐PCL) or MPEG‐b‐poly(L ‐lactide) (MPEG‐PLLA) diblock copolymers were prepared by the polymerization of CL or LA, using MPEG as an initiator in the presence of stannous octoate. MPEG‐b‐poly(ε‐caprolactone‐ran‐L ‐lactide) (MPEG‐PCLA) diblock copolymers with different chemical composition of PCL and PLLA were also prepared by adjusting the amount of CL and LA from MPEG in the presence of stannous octoate. In degradation study, the degradation of the MPEG‐PCLA diblock copolymers mainly depends on the PCL and PLLA segments present in their structure. MPEG‐PCLA, with intermediate ratio of PCL and PLLA segment, completely degraded after 14 weeks. Meanwhile, partially degraded MPEG‐PCLA segments and parent MPEG segments were observed at higher PCL or PLLA segment contents. Introduction of PLLA into the PCL segments caused a lowering of the crystallinity of the diblock copolymers, thus, inducing a faster incoming of water into the copolymers. We confirmed that the diblock copolymers, with lower degree of crystallinity, have degraded more rapidly. POLYM. ENG. SCI., 46: 1242–1249, 2006. © 2006 Society of Plastics Engineers     

Surface microphase separation in PDMS‐b‐PMMA‐b‐PHFBMA triblock copolymer films

Well‐defined poly(dimethylsiloxane)‐block‐poly(methyl methacrylate)‐block‐poly(2,2,3,3,4,4,4‐heptafluorobutyl methacrylate) (PDMS‐b‐PMMA‐b‐PHFBMA) triblock copolymers were synthesized via atom transfer radical polymerization (ATRP). Surface microphase separation in the PDMS‐b‐PMMA‐b‐PHFBMA triblock copolymer films was investigated. The microstructure of the block copolymers was investigated by transmission electron microscopy (TEM) and atomic force microscopy (AFM). Surface composition was studied by X‐ray photoelectron spectroscopy (XPS). The chemical composition at the surface was determined by the surface microphase separation in the PDMS‐b‐PMMA‐b‐PHFBMA triblock copolymer films. The increase of the PHFBMA content could strengthen the microphase separation behavior in the PDMS‐b‐PMMA‐b‐PHFBMA triblock copolymer films and reduce their surface tension. Comparison between the PDMS‐b‐PMMA‐b‐PHFBMA triblock copolymers and the PDMS‐b‐PHFBMA diblock copolymers showed that the introduction of the PMMA segments promote the fluorine segregation onto the surface and decrease the fluorine content in the copolymers with low surface energy. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis and characterization of copolymers with the same proportions of polystyrene and poly(ethylene oxide) compositions but different connection sequence by the efficient Williamson reaction

The AB type diblock PS‐b‐PEO and ABA type triblock PS‐b‐PEO‐b‐PS copolymers containing the same proportions of polystyrene (PS) and poly(ethylene oxide) (PEO) but different connection sequence were synthesized and investigated. Using the sequential living anionic polymerization and ring‐opening polymerization mechanisms, diblock PS‐b‐PEO copolymers with one hydroxyl group at the PEO end were obtained. Then, using the classic and efficient Williamson reaction (realized in a ‘click’ style), triblock PS‐b‐PEO‐b‐PS copolymers were achieved by a coupling reaction between hydroxyl groups at the PEO end of PS‐b‐PEO. The PS‐b‐PEO and PS‐b‐PEO‐b‐PS copolymers were well characterized by ¹H NMR spectra and SEC measurements. The critical micelle concentration (CMC) and thermal behaviors were also investigated by steady‐state fluorescence spectra and DSC, respectively. The results showed that, because the PEO segment in triblock PS‐b‐PEO‐b‐PS was more restricted than that in diblock PS‐b‐PEO copolymer, the former PS‐b‐PEO‐b‐PS copolymer always gave higher CMC values and lower crystallization temperature (T_c), melting temperature (T_m) and degree of crystallinity (X_c) parameters. © 2015 Society of Chemical Industry     

Preparation and characterization of amphiphilic block copolymer of polyacrylonitrile‐block‐poly(ethylene oxide)

The synthesis of polyacrylonitrile‐block‐poly(ethylene oxide) (PAN‐b‐PEO) diblock copolymers is conducted by sequential initiation and Ce(IV) redox polymerization using amino‐alcohol as the parent compound. In the first step, amino‐alcohol potassium with a protected amine group initiates the polymerization of ethylene oxide (EO) to yield poly(ethylene oxide) (PEO) with an amine end group (PEO‐NH₂), which is used to synthesize a PAN‐b‐PEO diblock copolymer with Ce(IV) that takes place in the redox initiation system. A PAN‐poly(ethylene glycol)‐PAN (PAN‐PEG‐PAN) triblock copolymer is prepared by the same redox system consisting of ceric ions and PEG in an aqueous medium. The structure of the copolymer is characterized in detail by GPC, IR, ¹H‐NMR, DSC, and X‐ray diffraction. The propagation of the PAN chain is dependent on the molecular weight and concentration of the PEO prepolymer. The crystallization of the PAN and PEO block is discussed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1753–1759, 2003     

Vesicular and micellar self‐assembly of stimuli‐responsive poly(N‐isopropyl acrylamide‐b‐9‐anthracene methyl methacrylate) amphiphilic diblock copolymers

Dually responsive amphiphilic diblock copolymers consisting of hydrophilic poly(N‐isopropyl acrylamide) [poly(NIPAAm)] and hydrophobic poly(9‐anthracene methyl methacrylate) were synthesized by reversible addition fragmentation chain‐transfer (RAFT) polymerization with 3‐(benzyl sulfanyl thiocarbonyl sulfanyl) propionic acid as a chain‐transfer agent. In the first step, the poly(NIPAAm) chain was grown to make a macro‐RAFT agent, and in the second step, the chain was extended by hydrophobic 9‐anthryl methyl methacrylate to yield amphiphilic poly(N‐isopropyl acrylamide‐b‐9‐anthracene methyl methacrylate) block copolymers. The formation of copolymers with three different hydrophobic block lengths and a fixed hydrophilic block was confirmed from their molecular weights. The self‐assembly of these copolymers was studied through the determination of the lower critical solution temperature and critical micelle concentration of the copolymers in aqueous solution. The self‐assembled block copolymers displayed vesicular morphology in the case of the small hydrophobic chain, but the morphology gradually turned into a micellar type when the hydrophobic chain length was increased. The variations in the length and chemical composition of the blocks allowed the tuning of the block copolymer responsiveness toward both the pH and temperature. The resulting self‐assembled structures underwent thermally induced and pH‐induced morphological transitions from vesicles to micelles and vice versa in aqueous solution. These dually responsive amphiphilic diblock copolymers have potential applications in the encapsulation of both hydrophobic and hydrophilic drug molecules, as evidenced from the dye encapsulation studies. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46474.     

Self‐assembled nanostructures: preparation,characterization, thermal,optical and morphological characteristics of amphiphilic diblock copolymers based on poly(2‐hydroxyethyl methacrylate‐block‐N‐phenylmaleimide)

A series of well‐defined amphiphilic poly[(2‐hydroxyethyl methacrylate)‐block‐(N‐phenylmaleimide)] diblock copolymers containing hydrophilic and hydrophobic blocks of different lengths were synthesized by atom transfer radical polymerization. The properties of the diblock copolymers and their ability to form large compound spherical micelles are described. Their optical, morphological and thermal properties and self‐assembled structure were also investigated. The chemical structure and composition of these copolymers have been characterized by elemental analysis, Fourier transform infrared, ¹H NMR, UV–visible and fluorescence spectroscopy, and size exclusion chromatography. Furthermore, the self‐assembly behavior of these copolymers was investigated by transmission electron microscopy and dynamic light scattering, which indicated that the amphiphilic diblock copolymer can self‐assemble into micelles, depending on the length of both blocks in the copolymers. These diblock copolymers gave rise to a variety of microstructures, from spherical micelles, hexagonal cylinders to lamellar phases. © 2013 Society of Chemical Industry     

An in vitro focus on doxorubicin hydrochloride delivery of novel pH‐responsive poly(2‐succinyloxyethylmethacrylate) and poly[(N‐4‐vinylbenzyl),N,N‐diethylamine] diblock copolymers

Novel pH‐responsive poly(2‐succinyloxyethylmethacrylate)‐b‐poly[(N‐4‐vinylbenzyl),N,N‐diethylamine] [poly(SEMA‐b‐VEA)] diblock copolymers were synthesized via reversible addition fragmentation transfer (RAFT) polymerization to investigate their self‐assembly micellar behavior. The self‐assembly behaviors of synthesized diblock copolymers with distinct molecular weights (labeled (1) to) were confirmed by ¹H NMR spectroscopy, TEM and dynamic light scattering measurements. Doxorubicin hydrochloride (DOX) loading capacity was evaluated, and the in vitro cytotoxicity effect of DOX‐loaded diblock copolymer was also studied by assessing the survival rate of the breast cancer cell line MCF‐7 with 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) assay. The results exhibited remarkable controlled release in the MTT assay. The DOX encapsulation efficiency was calculated to be 96.4%. The size and zeta potential of DOX‐loaded poly(SEMA‐b‐VEA) diblock copolymers were 204 nm and +5.7 mV at a pH of 7.4. DOX release values after 440 h at pH 7.4, 5.4 and 4 were 22.15%, 31.43% and 47.06%, respectively. The released values of DOX‐loaded poly(SEMA‐b‐VEA) and at pH 7.4 were 22.15%, 20.5% and 17.5%, respectively. Cell survival ratios were 18.9%, 23.16% and 16.92% after 72 h. Poly(SEMA‐b‐VEA) copolymers can be considered in nanomedicine applications due to their excellent pH‐responsive micellar behavior. © 2017 Society of Chemical Industry     

Synthesis of azobenzene‐containing side chain liquid crystalline diblock copolymers using RAFT polymerization and photo‐responsive behavior

Well‐defined azobenzene‐containing side chain liquid crystalline diblock copolymers composed of poly[6‐[4‐(4‐methoxyphenylazo)phenoxy]hexyl methacrylate] (PAzoMA) and poly(glycidyl methacrylate) (PGMA) were synthesized by a two‐step reversible addition–fragmentation chain transfer polymerization (RAFT). The thermal liquid‐crystalline phase behavior of the PGMA‐b‐PAzoMA diblock copolymers in bulk were measured by differential scanning calorimetry (DSC) and polarized light microscopy (POM). The synthesized diblock copolymers exhibited a smectic and nematic liquid crystalline phase over a relatively wide temperature range. With increasing the weight fraction of the PAzoMA block, the phase transition temperatures, and corresponding enthalpy changes increased. Atomic force microscope (AFM) measurements confirmed the formation of the microphase separation in PGMA‐b‐PAzoMA diblock copolymer thin films and the microphase separation became more obvious after cross‐linking the PGMA block. The photochemical transition behavior of the PGMA‐b‐PAzoMA diblock copolymers in solution and in thin films were investigated by UV–vis spectrometry. It was found that the trans–cis isomerization of diblock copolymers was slower than that of the corresponding PAzoMA homopolymer and the photoisomerization rates decreased with increasing either the length of PAzoMA block or PGMA block. The photo‐induced isomerization in solid films was quite different with that in CHCl₃ solution due to the aggregation of the azobenzene chromophore. The cross‐linking structures severely suppressed the photoisomerization of azobenzene chromophore. These results may provide guidelines for the design of effective photo‐responsive anisotropic materials. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2165–2175, 2013     

Synthesis and characterization of temperature‐sensitive block copolymers from poly(N‐isopropylacrylamide) and 4‐methyl‐ε‐caprolactone or 4‐phenyl‐ε‐caprolactone

This study synthesizes thermally sensitive block copolymers poly(N‐isopropylacrylamide)‐b‐poly(4‐methyl‐ε‐caprolactone) (PNIPA‐b‐PMCL) and poly(N‐isopropylacrylamide)‐b‐poly(4‐phenyl‐ε‐caprolactone) (PNIPA‐b‐PBCL) by ring‐opening polymerization of 4‐methyl‐ε‐caprolactone (MCL) or 4‐phenyl‐ε‐caprolactone (BCL) initiated from hydroxy‐terminated poly(N‐isopropylacrylamide) (PNIPA) as the macroinitiator in the presence of SnOct₂ as the catalyst. This research prepares a PNIPA bearing a single terminal hydroxyl group by telomerization using 2‐hydroxyethanethiol (ME) as a chain‐transfer agent. These copolymers are characterized by differential scanning calorimetry (DSC), ¹H‐NMR, FTIR, and gel permeation chromatography (GPC). The thermal properties (T_g) of diblock copolymers depend on polymer compositions. Incorporating larger amount of MCL or BCL into the macromolecular backbone decreases T_g. Their solutions show transparent below a lower critical solution temperature (LCST) and opaque above the LCST. LCST values for the PNIPA‐b‐PMCL aqueous solution were observed to shift to lower temperature than that for PNIPA homopolymers. This work investigates their micellar characteristics in the aqueous phase by fluorescence spectroscopy, transmission electron microscopy (TEM), and dynamic light scattering (DLS). The block copolymers formed micelles in the aqueous phase with critical micelle concentrations (CMCs) in the range of 0.29–2.74 mg L^?1, depending on polymer compositions, which dramatically affect micelle shape. Drug entrapment efficiency and drug loading content of micelles depend on block polymer compositions. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Amphiphilic 2‐ethyl hexyl methacrylate‐b‐N,N′‐dimethylacrylamide diblock copolymer monolayer behaviour at the air − water interface†

The surface activities of two amphiphilic diblock copolymers containing 2‐ethyl hexyl methacrylate‐b‐N,N′‐dimethylacrylamide (EHMA‐b‐DMA) possessing hydrophobic segments of different chain lengths were studied. Toward this end, surface pressure?area (π?A) isotherms, static and dynamic elasticities and the ν exponent of the excluded volume of polymers forming monolayers at the air?water interface were measured. The degree of hydrophobicity of the diblock copolymers was estimated by determining their surface energy values from contact angle measurements. The morphology of the monolayer at different surface pressures was studied by Brewster angle microscopy. Both copolymers were observed to form stable and elastic monolayers, and their collapse was observed to occur at similar surface pressures. Langmuir?Blodgett films were successfully deposited onto mica and silicon wafers and analysed by atomic force microscopy. © 2014 Society of Chemical Industry     

Synthesis and properties of polystyrene‐b‐poly(ethylene oxide)‐b‐polystyrene triblock copolymers

A series of well‐defined and property‐controlled polystyrene (PS)‐b‐poly(ethylene oxide) (PEO)‐b‐polystyrene (PS) triblock copolymers were synthesized by atom‐transfer radical polymerization, using 2‐bromo‐propionate‐end‐group PEO 2000 as macroinitiatators. The structure of triblock copolymers was confirmed by ¹H‐NMR and GPC. The relationship between some properties and molecular weight of copolymers was studied. It was found that glass‐transition temperature (T_g) of copolymers gradually rose and crystallinity of copolymers regularly dropped when molecular weight of copolymers increased. The copolymers showed to be amphiphilic. Stable emulsions could form in water layer of copolymer–toluene–water system and the emulsifying abilities of copolymers slightly decreased when molecular weight of copolymers increased. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 727–730, 2006     

Synthesis,photophysical properties and microphase separation of all‐conjugated diblock copolymers with hydrophilic side chains

A series of new all‐conjugated diblock copolymers, poly(2,5‐dioctyloxy‐p‐phenylene)‐block‐poly(3‐methoxyethoxyethoxy‐methylthiophene) (PPP‐b‐P3MEEMT), with hydrophilic side‐chains have been synthesized by quasi‐living Grignard metathesis polymerization. The narrow polydispersity indices of the block copolymers are in the range 1.32–1.40. The block ratios in the obtained diblock copolymers can be well defined by the feed ratios of the monomers. Photoluminescence results reveal that resonance energy transfer occurs from the PPP block to the P3MEEMT block in dilute solution. Differential scanning calorimetry shows that both PPP and P3MEEMT blocks in the copolymers produce crystalline regions and lead to microphase separation as indicated by two endothermal transitions, corresponding to the melting peaks of the PPP and P3MEEMT blocks, respectively. The formations of microphase‐separated nanostructures in annealed copolymer films are also observed using transmission electron microscopy. © 2012 Society of Chemical Industry     

Morphologies of an Amphiphilic Diblock Copolymer of Poly (Ethylene Oxide)-b-Polystyrene and Its Blends with Poly (2,6-Dimethyl-1,4-Oxide)

Systems containing block copolymers are of great interest due to the ability of copolymers to self-assemble into a variety of structured, ordered, or partially ordered morphologies. A fascinating morphology of two-dimensional arrays of hexagonal-like holes was observed for the first time in the diblock copolymer of poly (ethylene oxide)-b-polystyrene (PEO-b-PS) by transmission electron microscopy (TEM). The blends of PEO-b-PS with poly (2,6-dimethyl-1,4-phenylene oxide) (PPO) were obtained by solution blending, and the morphologies of PEO nano-dispersed particles in PPO/PS matrix were observed by atomic force microscopy (AFM) and TEM. Using the film forming technique on water/air interface, the core-shell morphology with PEO as shells was obtained in PEO-b-PS/PPO blends. Thus, three different morphologies were obtained by controlling preparation conditions. Especially, PEO-b-PS self-organized into the hexagonal-like holes patterns was first found to our knowledge.     

Synthesis of amphiphilic temperature‐sensitive poly(N‐isopropylacrylamide)‐block‐poly(tetramethylene carbonate) block copolymers and micellar characterization

Amphiphilic thermally sensitive poly(N‐isopropylacrylamide)‐block‐poly(tetramethylene carbonate) block copolymers were synthesized by ring‐opening polymerization of tetramethylene carbonate with hydroxyl‐terminated poly(N‐isopropylacrylamide) (PNiPAAm) as macro‐initiator in the presence of stannous octoate as catalyst. The synthesis involved PNiPAAm bearing a single terminal hydroxyl group prepared by telomerization using 2‐hydroxyethanethiol as a chain‐transfer agent. The copolymers were characterized using ¹H NMR and Fourier transform infrared spectroscopy and gel permeation chromatography. Their solutions show reversible changes in optical properties: transparent below the lower critical solution temperature (LCST) and opaque above the LCST. The LCST depends on the polymer composition and the media. Owing to their amphiphilic characteristics, the block copolymers form micelles in the aqueous phase with critical micelle concentrations (CMCs) in the range 1.11–22.9 mg L^?1. Increasing the hydrophobic segment length or decreasing the hydrophilic segment length in the amphiphilic diblock copolymers produces lower CMCs. A core‐shell structure of the micelles is evident from ¹H NMR analyses of the micelles in D₂O. Transmission electron microscopic analyses of micelle morphology show a spherical structure of both blank and drug‐loaded micelles. The blank and drug‐loaded micelles have an average size of less than 130 nm. Observations show high drug‐entrapment efficiency and drug‐loading content for the drug‐loaded micelles. Copyright © 2010 Society of Chemical Industry     

Chemoenzymatic synthesis of the novel amphiphilic diblock copolymer poly[caprolactone‐block‐(glycidyl methacrylate)] from a bifunctional initiator and its micellization behavior

The chemoenzymatic synthesis of a novel diblock copolymer consisting of a hydrocarbon block of polycaprolactone (PCL) and an epoxy‐based block of poly(glycidyl methacrylate) (PGMA) was achieved by the combination of enzymatic ring‐opening polymerization (eROP) and atom transfer radical polymerization (ATRP). A trichloromethyl‐terminated PCL macrointiator was obtained via Novozyme 435‐catalyzed eROP of ε‐caprolactone from a bifunctional initiator, 2,2,2‐trichloroethanol, under anhydrous conditions. PCL‐b‐PGMA diblock copolymers were synthesized in a subsequent ATRP of glycidyl methacrylate. The kinetics analysis of ATRP indicated a ‘living’/controlled radical polymerization. The macromolecular structure and thermal properties of the PCL macroinitiator and of the diblock copolymer were characterized using NMR spectroscopy, gel permeation chromatography and differential scanning calorimetry. The well‐defined PCL‐b‐PGMA amphiphilic diblock copolymer self‐assembled in aqueous solution into nanoscale micelles. The size and shape of the resulting micelles were investigated using dynamic light scattering, transmission electron microscopy and tapping‐mode atomic force microscopy. Copyright © 2007 Society of Chemical Industry     

Polyethylene‐b‐poly(ethylene glycol) diblock copolymers: New synthetic strategy and application

Polyethylene‐b‐poly (ethylene glycol) (PE‐b‐PEG) was successfully synthesized by a coupling reaction of hydroxyl‐terminated polyethylene (PE‐OH) and isocyanate‐terminated poly (ethylene glycol) (PEG‐NCO). PE‐OH was prepared by coordination chain transfer polymerization (CCTP) using 2,6‐bis[1‐(2,6‐diisopropylphenyl)imino ethyl] pyridine iron (II) dichloride /dry ethylaluminoxane (DEAO) /diethyl zinc (ZnEt₂) as catalyst and subsequent in situ oxidation with oxygen. The active centers of this catalyst system were counted, indicating that the active centers were more stable using DEAO as cocatalyst than using dry methylaluminoxane (DMAO) as cocatalyst. PEG‐NCO was synthesized through the condensation reaction of monomethylpoly(ethylene glycol) (PEG) with isophoronediisocyanate (IPDI). Subsequently, the thermal characterization, morphological characterization and the application of these diblock copolymers was investigated. The results indicated that the diblock copolymers were effective compatilizers for polyethylene/poly(ethylene glycol) blends. Meanwhile, they were excellent surface modification agents for polyethylene membrane and glass sheet, it can efficiently turn a hydrophobic surface into a hydrophilic surface, or vice versa. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42236.     

Self‐assembly and degradation of poly[(2‐methacryloyloxyethyl phosphorylcholine)‐block‐(D,L‐lactide)] diblock copolymers: large compound micelles to vesicles

Biodegradable poly[(2‐methacryloyloxyethyl phosphorylcholine)‐block‐(D ,L ‐lactide)] (PMPC‐b‐PLA) diblock copolymers with various hydrophilic PMPC weight fractions (f_PC) will spontaneously self‐assemble into well‐defined vesicles and large compound micelles (LCMs) in water. Transmission electron microscopy, scanning electron microscopy, dynamic light scattering and fluorescence microscopy were used to observe their aggregate morphologies. The degradation of the LCMs was investigated and the loss of molecular weight of PLA blocks was confirmed using ¹H NMR analysis. The hydrolysis of PLA increases f_PC and consequently shifts the preferred morphology from LCMs to vesicles. Such degradation‐induced morphological transitions mean that the biocompatible and biodegradable LCMs have great application potential in drug delivery. Copyright © 2010 Society of Chemical Industry