CO2‐Activated Reversible Transition between Polymersomes and Micelles with AIE Fluorescence

Fluorescent polymersomes with both aggregation‐induced emission (AIE) and CO₂‐responsive properties were developed from amphiphilic block copolymer PEG‐b‐P(DEAEMA‐co‐TPEMA) in which the hydrophobic block was a copolymer made of tetraphenylethene functionalized methacrylate (TPEMA) and 2‐(diethylamino)ethyl methacrylate (DEAEMA) with unspecified sequence arrangement. Four block copolymers with different DEAEMA/TPEMA and hydrophilic/hydrophobic ratios were synthesized, and bright AIE polymersomes were prepared by nanoprecipitation in THF/water and dioxane/water systems. Polymersomes of PEG₄₅‐b‐P(DEAEMA₃₆‐co‐TPEMA₆) were chosen to study the CO₂‐responsive property. Upon CO₂ bubbling vesicles transformed to small spherical micelles, and upon Ar bubbling micelles returned to vesicles with the presence of a few intermediate morphologies. These polymersomes might have promising applications as sensors, nanoreactors, or controlled release systems.     

Construction of PIB‐b‐PDEAEMA well‐defined amphiphilic diblock copolymers via sequential living carbocationic and RAFT polymerization

A series of well‐defined amphiphilic diblock copolymers consisting of hydrophobic polyisobutylene (PIB) and hydrophilic poly(2‐(diethylamino)ethyl methacrylate) (PDEAEMA) segments was synthesized via the combination of living carbocationic polymerization and reversible addition fragmentation chain transfer (RAFT) polymerization. Living carbocationic polymerization of isobutylene followed by end‐capping with 1,3‐butadiene was first performed at ?70 °C to give a well‐defined allyl‐Cl‐terminated PIB with a low polydispersity (M_w/M_n =1.29). This end‐functionalized PIB was further converted to a macromolecular chain transfer agent for mediating RAFT block copolymerization of 2‐(diethylamino)ethyl methacrylate at 60 °C in tetrahydrofuran to afford the target well‐defined PIB‐b‐PDEAEMA diblock copolymers with narrow molecular weight distributions (M_w/M_n ≤1.22). The self‐assembly behavior of these amphiphilic diblock copolymers in aqueous media was investigated by fluorescence spectroscopy and transmission electron microscope, and furthermore, their pH‐responsive behavior was studied by UV‐vis and dynamic light scattering. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1478–1486     

Polyisobutylene‐b‐Poly(N,N‐diethylacrylamide) well‐defined amphiphilic diblock copolymer: Synthesis and thermo‐responsive phase behavior

Polyisobutylene‐b‐poly(N,N‐diethylacrylamide) (PIB‐b‐PDEAAm) well‐defined amphiphilic diblock copolymers were synthesized by sequential living carbocationic polymerization and reversible addition‐fragmentation chain transfer (RAFT) polymerization. The hydrophobic polyisobutylene segment was first built by living carbocationic polymerization of isobutylene at ?70 ° C followed by multistep transformations to give a well‐defined (M_w/M_n = 1.22) macromolecular chain transfer agent, PIB‐CTA. The hydrophilic poly(N,N‐diethylacrylamide) block was constructed by PIB‐CTA mediated RAFT polymerization of N,N‐diethylacrylamide at 60 ° C to afford the desired well‐defined PIB‐b‐PDEAAm diblock copolymers with narrow molecular weight distributions (M_w/M_n ≤1.26). Fluorescence spectroscopy, transmission electron microscope, and dynamic light scattering (DLS) were employed to investigate the self‐assembly behavior of PIB‐b‐PDEAAm amphiphilic diblock copolymers in aqueous media. These diblock copolymers also exhibited thermo‐responsive phase behavior, which was confirmed by UV‐Vis and DLS measurements. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1143–1150     

Exploring amino acid‐tethered polymethacrylates as CO2‐sensitive macromolecules: A concealed property

Carbon dioxide (CO₂)‐responsive polymers have been gaining considerable interest because of their reactions with CO₂, giving rise to gas‐switchable properties, which can easily be reversed by mild heating or purging with inert gases. Herein, the synthesis of a series of side‐chain amino acids (alanine, leucine, isoleucine, phenylalanine, tryptophan) appending poly(meth)acrylates carrying primary amine (? NH₂) groups via reversible addition‐fragmentation chain transfer (RAFT) polymerization method was reported. It was found that alanine, leucine, isoleucine containing polymers displayed solubility–insolubility transition behavior and their associated property changes (solution transmittance, electrical conductivity, pH, zeta potential, and hydrodynamic diameter) in water upon alternate bubbling of CO₂/N₂ at room temperature. Among the three CO₂‐sensitive polymers only leucine based macromolecule was further chain extended with a thermoresponsive motif, di(ethylene glycol) methyl ether methacrylate (DEGMMA), via RAFT polymerization. CO₂‐tunable lower critical solution temperature and self‐assembling behavior of the diblock copolymer was carefully examined by UV–vis, ¹H NMR spectroscopy, dynamic light scattering (DLS), and field emission‐scanning electron microscopy (FE‐SEM) to establish dual thermo and gas‐tunable flip–flop micellizaion from the as‐synthesized block copolymer. Formation of polyammonium methacrylate bearing bicarbonate as counter anion is responsible for pendant primary amine containing polymer induced CO₂‐responsiveness. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2794–2803     

Light‐driven and aggregation‐induced emission from side‐chain azoindazole polymers

The well‐defined azoindazole‐containing homopolymer, poly(6‐{6‐[(4‐dimethylamino) phenylazo]‐indazole}‐hexyl methacrylate) (PDHMA), and amphiphilic diblock copolymer, poly({6‐[6‐(4‐dimethylamino)phenylazo]‐indazole}‐hexyl methacrylate)‐b‐poly(2‐(dimethylamino)ethylmethacrylate) (PDHMA_m‐b‐PDMAEMA_n), were successfully prepared via reversible addition‐fragmentation chain transfer polymerization technique. The homopolymer and amphiphilic diblock copolymer in CH₂Cl₂ exhibited intense fluorescence emission accompanied by trans–cis photoisomerization of azoindazole group under UV irradiation. The experiment results indicated that the intense fluorescence emission may be attributed to an inhibition of photoinduced electron transfer of the cis form of azoindazole. On the other hand, the intense fluorescence emission of amphiphilic diblock copolymers in water‐tetrahydrofuran mixture was observed, which increased with the volume ratio of water in the mixed solvent. The self‐aggregation behaviors of three amphiphilic diblock copolymers were examined by transmission electron microscopy, laser light scattering, and UV–vis spectra. The restriction of intramolecular rotation of the azoindazole groups in aggregates was considered as the main cause of aggregation‐induced fluorescence emission. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011.     

Influence of the polymer structure over self‐assembly and thermo‐responsive properties: The case of PEG‐b‐PCL grafted copolymers via a combination of RAFT and ROP

During the last years, the field of drug delivery has experienced a growing interest toward the so‐called thermo‐responsive polymers: synthetic materials that, due to the specific hydrophilic–lipophilic balance of their repeating units, exhibit a lower critical solution temperature (LCST) in water associated to a characteristic coil–globule transition. In this work, thermo‐responsive amphiphilic block copolymers are synthesized via reversible addition‐fragmentation transfer (RAFT) polymerization starting from thermo‐responsive monomers and a hydrophobic biodegradable macromonomer, oligo(caprolactone)methacrylate (CL₃MA), produced via ring opening polymerization (ROP). The obtained copolymers exhibit an interesting self‐assembly behavior leading to nanoparticles (NPs) as long as temperature is kept below the LCST. Otherwise, once this value is overcome, the destabilization of the NPs causes the formation of hydrophobic superstructures that enhance the release of an entrapped lipophilic drug. This characteristic behavior has been systematically studied and related to the copolymer structure. In particular, the self‐assembly behavior as well as temperature‐triggered NP destabilization have been related to the relative length of the two blocks constituting the copolymers and to their hydrophilic–lipophilic balance (HLB). Finally, the efficacy of the thermo‐responsive triggered drug release has been tested in the case of Paclitaxel (PTX). © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2919–2931     

Reversible addition–fragmentation chain transfer synthesis of amidine‐based,CO2‐responsive homo and AB diblock (Co)polymers comprised of histamine and their gas‐triggered self‐assembly in water

Well‐defined homopolymers of pentafluorophenyl acrylate (PFPA) and AB diblock copolymers of N,N‐dimethylacrylamide (DMA) and poly(ethylene glycol) methyl ether acrylate (PEGA) with PFPA were prepared by reversible addition–fragmentation chain transfer (RAFT) radical polymerization. Three PFPA homopolymers of different molecular weights were reacted with the commercially available amidine and guanidine species histamine (HIS) dihydrochloride and L ‐arginine methyl ester (ARG) dihydrochloride in the presence of S‐methyl methanethiosulfonate to yield, quantitatively, the corresponding amidine and guanidine‐based acrylamido homopolymers. Both the HIS and ARG homopolymers are known to reversibly bind CO₂ with, in the case of the former, CO₂ fixation being accompanied with a switch from a hydrophobic to hydrophilic state. The RAFT synthesis of PFPA‐DMA and PEGA‐PFPA diblock copolymers yielded well‐defined materials with a range of molar compositions. These precursor materials were converted to the corresponding HIS and ARG block copolymers whose structure was confirmed using ¹H NMR spectroscopy. Employing a combination of dynamic light scattering and transmission electron microscopy, we demonstrate that the DMA‐HIS and PEGA‐HIS diblock copolymers are able to undergo reversible and cyclable self‐directed assembly in aqueous media using CO₂ and N₂ as the triggers between fully hydrophilic and amphiphilic (assembled) states. For example, in the case of the 54:46 DMA‐HIS diblock, aggregates with hydrodynamic diameters of about 40.0 nm are readily formed from the molecularly dissolved state. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Fluorescence emission of amphiphilic copolymers bearing benzimidazole groups: Stimuli‐responsive behaviors in aqueous solution

A stimuli‐responsive amphiphilic copolymer poly(NIPAM_m‐b‐VBNBI_n), including N‐isopropylacrylamide (NIPAM) as a thermoresponsive unit and 1‐(4‐vinyl benzyl)‐2‐naphthyl‐benzimidazole (VBNBI) as a sensitive fluorophore unit, was designed and synthesized by reversible addition‐fragmentation chain transfer polymerization. The aqueous solutions of the copolymers exhibited reversible fluorescent response to pH and temperature. In addition, the copolymers showed aggregation‐induced fluorescence enhancement in THF/water mixture. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4459–4466     

Thermoresponsive terpolymers based on methacrylate monomers: Effect of architecture and composition

A series of amphiphilic thermoresponsive copolymers was synthesized by group transfer polymerization. Seven copolymers were prepared based on the nonionic hydrophobic n‐butyl methacrylate (BuMA), the ionizable hydrophilic and thermoresponsive 2‐(dimethylamino)ethyl methacrylate (DMAEMA) and the nonionic hydrophilic poly(ethylene glycol)methyl methacrylate (PEGMA). In particular, one diblock copolymer and six tricomponent copolymers of different architectures and compositions, one random and five triblock copolymers, were synthesized. The polymers and their precursors were characterized in terms of their molecular weight and composition using gel permeation chromatography and proton nuclear magnetic resonance spectroscopy, respectively. Aqueous solutions of the polymers were studied by turbidimetry, hydrogen ion titration, and light scattering to determine their cloud points, pK_as, and hydrodynamic diameters and investigate the effect of the polymers' composition and architecture. The thermoresponsive behavior of the copolymers was also studied. By increasing the temperature, all polymer solutions became more viscous, but only one polymer, the one with the highest content of the hydrophobic BuMA, formed a stable physical gel. Interestingly, the thermoresponsive behavior of these triblock copolymers was affected not only by the terpolymers' composition but also by the terpolymers' architecture. These findings can facilitate the design and engineering of injectable copolymers for tissue engineering that could enable the in situ formation of physical gels at body temperature. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 775–783, 2010     

Preparation of CO2‐switchable latexes using N‐[3‐(dimethylamino)propyl]‐methacrylamide (DMAPMAm)

CO₂‐switchable polystyrene (PS), poly(methyl methacrylate) (PMMA), and poly(butyl methacrylate) (PBMA) latexes were prepared via surfactant‐free emulsion polymerization (SFEP) under a CO₂ atmosphere, employing N‐[3‐(dimethylamino)propyl]methacrylamide (DMAPMAm) as a CO₂‐switchable, water‐soluble, and hydrolytically stable comonomer. The conversion of the SFEP of styrene reaches >95% in less than 5 h. The resulting latexes have near monodisperse particles (PDI ≤ 0.05), as confirmed by DLS and TEM. The latexes could be destabilized by bubbling nitrogen (N₂) and heating at 65 °C for 30 min, and easily redispersed by only bubbling CO₂ for a short time without using sonication. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 1059–1066     

Synthesis of chiral amphiphilic diblock copolymers via consecutive RAFT polymerizations and their aggregation behavior in aqueous solution

Two chiral amphiphilic diblock copolymers with different relative lengths of the hydrophobic and hydrophilic blocks, poly(6‐O‐p‐vinylbenzyl‐1,2:3,4‐Di‐O‐isopropylidene‐D ‐galactopyranose)‐b‐poly(N‐isopropylacrylamide) or poly(VBCPG)‐b‐poly(NIPAAM) and poly(20‐(hydroxymethyl)‐pregna‐1,4‐dien‐3‐one methacrylate)‐b‐poly(N‐isopropylacrylamide) or poly(MAC‐HPD)‐b‐poly(NIPAAM) were synthesized via consecutive reversible addition‐fragmentation chain‐transfer polymerizations of VBCPG or MAC‐HPD and NIPAAM. The chemical structures of these diblock copolymers were characterized by ¹H nuclear magnetic resonance spectroscopy. These amphiphilic diblock copolymers could self‐assemble into micelles in aqueous solution, and the morphologies of micelles were investigated by transmission electron microscopy. By comparison with the lower critical solution temperatures (LCST) of poly(NIPAAM) homopolymer in deionized water (32 °C), a higher LCST of the chiral amphiphilic diblock copolymer (poly(VBCPG)‐b‐poly(NIPAAM)) was observed and the LCST increased with the relative length of the poly(VBCPG) block in the copolymer from 35 to 47 °C, respectively. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7690–7701, 2008     

Tuning amphiphilicity/temperature‐induced self‐assembly and in‐situ disulfide crosslinking of reduction‐responsive block copolymers

New poly(ethylene oxide)‐based block copolymers (ssBCs) with a random copolymer block consisting of a reduction‐responsive disulfide‐labeled methacrylate (HMssEt) and a thermoresponsive di(ethylene glycol)‐containing methacrylate (MEO₂MA) units were synthesized. The ratio of HMssEt/MEO₂MA units in the random P(MEO₂MA‐co‐HMssEt) copolymer block enables the characteristics of well‐defined ssBCs to be amphiphilic or thermoresponsive and double hydrophilic. Their amphiphilicity or temperature‐induced self‐assembly results in nanoaggregates with hydrophobic cores having different densities of pendant disulfide linkages. The effect of disulfide crosslinking density on morphological variation of disulfide‐crosslinked nanogels is investigated. In response to reductive reactions, the partial cleavage of pendant disulfide linkages in the hydrophobic cores converts the physically associated aggregates to disulfide‐crosslinked nanogels. The occurrence of in‐situ disulfide crosslinks provides colloidal stability upon dilution. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2057–2067     

Synthesis and characterization of polycholesteryl methacrylate–polyhydroxyethyl methyacrylate block copolymers

We report the synthesis and characterization of a series of novel diblock copolymers, poly(cholesteryl methacrylate‐b‐2‐hydroxyethyl methacrylate) (PCMA‐b‐PHEMA). Monomers, cholesteryl methacrylate (CMA) and 2‐(trimethylsiloxy)ethyl methacrylate (HEMA‐TMS), were prepared from methyacryloyl chloride and 2‐hydroxyethyl methacrylate, respectively. Homopolymers of CMA, PCMA, with well‐defined molecular weights and polydispersity indices (PDI), were prepared by reversible addition fragmentation and chain transfer (RAFT) method. Precursor diblock copolymers, PCMA‐b‐P(HEMA‐TMS), were synthesized using PCMA as macromolecular chain transfer agent and monomer, HEMA‐TMS. Product diblock copolymers, PCMA‐b‐PHEMA, were prepared by deprotecting trimethylsilyl units in the precursor diblock copolymers using acid catalysts. Detailed molecular characterization of the precursor diblock copolymers, PCMA‐b‐P(HEMA‐TMS), and the product diblock copolymers, PCMA‐b‐PHEMA, confirmed the composition and structure of these polymers. This versatile synthetic strategy can be used to prepare new amphiphilic block copolymers with cholesterol in one block and hydrogen‐bonding moieties in the second block. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6801–6809, 2008     

A successive route to amphiphilic graft copolymers with a hydrophilic poly(3‐hydroxypropyl methacrylate) backbone and hydrophobic polystyrene side chains

A successive method for preparing novel amphiphilic graft copolymers with a hydrophilic backbone and hydrophobic side chains was developed. An anionic copolymerization of two bifunctional monomers, namely, allyl methacrylate (AMA) and a small amount of glycidyl methacrylate (GMA), was carried out in tetrahydrofuran (THF) with 1,1‐diphenylhexyllithium (DPHL) as the initiator in the presence of LiCl ([LiCl]/[DPHL]₀ = 2), at −50 °C. The copolymer poly(AMA‐co‐GMA) thus obtained possessed a controlled molecular weight and a narrow molecular weight distribution (M_w /M_n = 1.08–1.17). Without termination and polymer separation, a coupling reaction between the epoxy groups of this copolymer and anionic living polystyrene [poly(St)] at −40 °C generated a graft copolymer with a poly(AMA‐co‐GMA) backbone and poly(St) side chains. This graft copolymer was free of its precursors, and its molecular weight as well as its composition could be well controlled. To the completed coupling reaction solution, a THF solution of 9‐borabicyclo[3.3.1]nonane was added, and this was followed by the addition of sodium hydroxide and hydrogen peroxide. This hydroboration changed the AMA units of the backbone to 3‐hydroxypropyl methacrylate, and an amphiphilic graft copolymer with a hydrophilic poly(3‐hydroxypropyl methacrylate) backbone and hydrophobic poly(St) side chains was obtained. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1195–1202, 2000     

Novel polymers based on atom transfer radical polymerization of 2‐methoxyethyl acrylate

Atom transfer radical polymerization (ATRP) has been employed in the polymerization of 2‐methoxyethyl acrylate (MEA) initiated by ethyl 2‐bromoisobutyrate in bulk or in toluene solution at 90–95 °C with the catalytic systems Cu(I)Br/PMDETA or HMTETA. Kinetics investigations revealed that ATRP of MEA proceeds in a controlled manner with a first‐order plot of monomer consumption, an almost linear molecular weight evolution and polydispersities < 1.29 in the entire conversion range. Well‐defined diblock copolymers with PMMA, PMEA‐b‐PMMA have been produced by use of both PMEA and PMMA macroinitiators, however, for the latter the controlled conditions were somehow difficult to maintain. The amphiphilic behavior of the diblock copolymers lead to phase separation resulting in two glass transition temperatures as detected by DSC. Contact angle (Θ) investigations with water on PMEA, PMMA, and diblock copolymers surfaces reveal PMEA as an intermediate hydrophilic with Θ ～ 50°, whereas PMMA and the diblock copolymers all fall in the hydrophobic region with Θ > 70°. © 2006 Wiley Periodicals, Inc. J Polym Sci Part Polym Chem45: 333–340, 2007     

Multi‐stimuli‐responsive self‐immolative polymer assemblies

Self‐immolative polymers (SIPs) undergo depolymerization in response to the cleavage of stimuli‐responsive end‐caps from their termini. Some classes of SIPs, including polycarbamates, have depolymerization rates that depend on environmental factors such as solvent and pH. In previous work, hydrophobic SIPs have been incorporated into amphiphilic block copolymers and used to prepare nanoassemblies. However, stimuli‐responsive hydrophilic blocks have not previously been incorporated. In this work, we synthesized amphiphilic copolymers composed of a hydrophobic polycarbamate SIP block and a hydrophilic poly(2‐(dimethylamino)ethyl methacrylate) (PDMAEMA) block connected by a UV light‐responsive linker end‐cap. It was hypothesized that after assembly of the block copolymers into nanoparticles, chain collapse of the PDMAEMA above its lower critical solution temperature (LCST) might change the environment of the SIP block, thereby altering its depolymerization rate. Self‐assembly of the block copolymers was performed, and the depolymerization of the resulting assemblies was studied by fluorescence spectroscopy, dynamic light scattering, and NMR spectroscopy. At 20 °C, the system exhibited a selective response to the UV light. At 65 °C, above the LCST of PDMAEMA, the systems underwent more rapid depolymerization, suggesting that the increase in rate arising from the higher temperature dominated over environmental effects arising from chain collapse. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 1868–1877     

Soft nanoparticles assembled from linear poly(ethylene glycol) and linear brush polydimethylsiloxane diblock copolymers

A series of novel amphiphilic diblock copolymers composed of hydrophilic linear poly(ethylene glycol) (PEG) and linear brush hydrophobic polydimethylsiloxane (PDMS) were synthesized. Three different molecular weights of monomethyl ether PEG were initially functionalized with 2‐bromoisobutyryl bromide to afford macroinitiators suitable for atom‐transfer radical polymerization. The macroinitiators were characterized by gel permeation chromatography, ¹H and ¹³C nuclear magnetic resonance spectroscopic analysis and matrix‐assisted laser desorption ionization time‐of‐flight mass spectroscopy. The three different molecular weight macroinitiators were then chain extended with monomethacryloxypropyl‐terminated PDMS and photoactive 2‐(methylacyloyloxy)ethyl anthracene‐9‐carboxylate in different molar ratios to afford a series of photoresponsive amphiphilic diblock copolymers with high conversions. Self‐assembly of these linear–linear brush diblock copolymers in N,N‐dimethylformamide afforded nanoparticles with hydrodynamic diameters (d_H) ranging from 41 to 268 nm, as determined by dynamic light scattering analysis. Crosslinking and stabilization of the nanoparticles was achieved via [4+4] photodimerization of the anthracene moieties upon exposure to UV radiation at 365 nm with the reverse reaction studied at a wavelength of 254 nm. Transmission electron microscopy revealed that the self‐assembled nanoparticles and their crosslinked derivatives had spherical morphologies. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1251–1262     

Novel temperature‐ and pH‐responsive graft copolymers composed of poly(L‐glutamic acid) and poly(N‐isopropylacrylamide)

A series of novel temperature‐ and pH‐responsive graft copolymers, poly(L ‐glutamic acid)‐g‐poly(N‐isopropylacrylamide), were synthesized by coupling amino‐semitelechelic poly(N‐isopropylacrylamide) with N‐hydroxysuccinimide‐activated poly(L ‐glutamic acid). The graft copolymers and their precursors were characterized, by ESI‐FTICR Mass Spectrum, intrinsic viscosity measurements and proton nuclear magnetic resonance (¹H NMR). The phase‐transition and aggregation behaviors of the graft copolymers in aqueous solutions were investigated by the turbidity measurements and dynamic laser scattering. The solution behavior of the copolymers showed dependence on both temperature and pH. The cloud point (CP) of the copolymer solution at pH 5.0–7.4 was slightly higher than that of the solution of the PNIPAM homopolymer because of the hydrophilic nature of the poly(glutamic acid) (PGA) backbone. The CP markedly decreased when the pH was lowered from 5 to 4.2, caused by the decrease in hydrophilicity of the PGA backbone. At a temperature above the lower critical solution temperature of the PNIPAM chain, the copolymers formed amphiphilic core‐shell aggregates at pH 4.5–7.4 and the particle size was reduced with decreasing pH. In contrast, larger hydrophobic aggregates were formed at pH 4.2. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4140–4150, 2008     

Novel perfluorocyclobutyl aryl ether‐based well‐defined amphiphilic block copolymer

A series of fluorine‐containing amphiphilic diblock copolymers comprising hydrophobic poly(p‐(2‐(p‐tolyloxy)perfluorocyclobutoxy)phenyl methacrylate) (PTPFCBPMA) and hydrophilic poly(2‐(diethylamino)ethyl methacrylate) (PDEAEMA) segments were synthesized via successive reversible addition fragmentation chain transfer (RAFT) polymerizations. RAFT homopolymerization of p‐(2‐(p‐tolyloxy)perfluorocyclobutoxy)phenyl methacrylate was first initiated by 2,2′‐azobisisobutyronitrile using cumyl dithiobenzoate as chain transfer agent, and the results show that the procedure was conducted in a controlled way as confirmed by the fact that the number‐average molecular weights increased linearly with the conversions of the monomer while the polydispersity indices kept below 1.30. Dithiobenzoate‐capped PTPFCHPMA homopolymer was then used as macro‐RAFT agent to mediate RAFT polymerization of 2‐(diethylamino)ethyl methacrylate, which afforded PTPFCBPMA‐b‐PDEAEMA amphiphilic diblock copolymers with different block lengths and narrow molecular weight distributions (M_w/M_n ≤ 1.28). The critical micelle concentrations of the obtained amphiphilic diblock copolymers were determined by fluorescence spectroscopy technique using N‐phenyl‐1‐naphthylamine as probe. The morphology and size of the formed micelles were investigated by transmission electron microscopy and dynamic light scattering, respectively. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

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