One‐Pot Template‐Free Synthesis of Monodisperse Hollow Hydrogel Microspheres and their Resulting Properties

Monodisperse poly(methacrylic acid/ethyleneglycoldimethacrylate) (MAA/EGDMA) hollow microcapsules, which exhibit pH‐responsive behavior, are prepared by diffusion of cationic surfactants and hydrophobic interaction. During the association of the negatively charged hydrogel microspheres and an oppositely charged surfactant (cetyltrimethylammonium bromide, CTA(+)B), the hydrophobic polymer‐surfactant complexes that form are separated from the internal water; consequently, a hollow structure can be formed. Confocal laser scanning microscopy, UV spectro­scopy and zeta potential are employed to study the formation of the hollow structure during the diffusion of the cationic surfactant. The controlled release behavior of methylene blue as a model drug from the as‐prepared poly(MAA/EGDMA) microcapsules with a hollow structure is investigated under different pH conditions. The hollow structure can be retained, even during repetitive pH changes.

     

Synthesis of Block Copolymers of 2‐Ethylhexyl Methacrylate,n‐Hexyl Methacrylate and Methyl Methacrylate via Anionic Polymerization at Ambient Temperature

It still remains a concern to break through the bottlenecks of anionic polymerization of polar monomers, such as side reactions, low conversion and low temperature (–78°C). In this work, potassium tert‐butoxide (t‐BuOK) was chosen to initiate the anionic polymerization of 2‐ethylhexyl methacrylate (EHMA) in tetrahydrofuran. The conversions were above 99% at 0 or 30°C, and above 95% at 60°C without side reaction inhibitors. The high conversions implied t‐BuOK could suppress the side reactions. A series of block copolymers of EHMA, n‐hexyl methacrylate (HMA) and methyl methacrylate (MMA) were further synthesized at 0°C, and the conversions were all above 99%. The GPC and ¹H NMR results confirmed the successful synthesis of the block copolymers. The molecular size of monomer and the state of t‐BuOK (free ion pairs or aggregates) remarkably affected the polymerization rates and the molecular structures of the products. The DMA results indicated that the glass transition temperatures of PEHMA or PHMA block and PMMA block were 20°C and 60°C, respectively, which deviated from –2°C and 105°C of homopolymer, respectively, due to the partial compatibility of the blocks. This work explored a route of the anionic polymerization of polar monomers at room temperature.     

Synthesis and asymmetric polymerization of (S)‐N‐maleoyl‐L‐leucine propargyl ester

A kind of N‐substituted maleimide (RMI), chiral (S)‐N‐maleoyl‐L ‐leucine propargyl ester ((S)‐PLMI) with a specific rotation of [α]₄₃₅ = ?27.5° was successfully synthesized from maleic anhydride, L ‐leucine, and propargyl alcohol. (S)‐PLMI was polymerized by three polymerization methods to obtain the corresponding optically active polymers. Asymmetric anionic, radical, and transition‐metal‐catalyzed polymerizations were carried out using organometal/chiral ligands, 2,2′‐azobisisobutyronitrile (AIBN) and (bicyclo [2,2,1]hepta‐2,5‐diene) chloro rhodium (I) dimer ([Rh(nbd) Cl]₂), respectively. Poly((S)‐PLMI) obtained by [Rh(nbd)Cl]₂ in DMF showed the highest specific rotation of ?280.6°. Chiroptical properties and structures of the polymers obtained were investigated by GPC, CD, IR, and NMR measurements. Two types of poly((S)‐PLMI)‐bonded‐silica gels as the chiral stationary phase (CSP) were prepared for high‐performance liquid chromatography (HPLC). Their optical resolution abilities were also elucidated. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3722–3738, 2007     

Synthesis of asymmetrically substituted head‐to‐head polyacetylenes from 2,3‐disubstituted‐1,3‐butadienes

Asymmetrically substituted head‐to‐head polyacetylenes with phenyl and triphenylamine, thienyl or pyrenyl side groups were synthesized through anionic or controlled radical polymerization of 2,3‐disubstituted‐1,3‐butadienes and subsequent dehydrogenation process. Anionic polymerizations of the designed monomers bearing pendent triphenylamine and thienyl group gave narrow disperse disubstituted precursor polybutadienes with exclusive 1,4‐ or 4,1‐structure, which were confirmed by GPC and NMR measurements. In addition, the monomers possessing pyrenyl group were polymerized via nitroxide mediated radical polymerization and the resulting polymers were obtained with controlled molecular weight and low polydispersities. These polybutadiene precursors were then dehydrogenated in the presence of 2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone. Thus asymmetrically substituted head‐to‐head polyacetylenes were obtained as indicated by ¹H NMR. The properties of polybutadiene precursors and the corresponding polyacetylenes were analyzed by UV–vis, DSC, and TGA. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 395–402     

One‐Pot Automated Synthesis of Quasi Triblock Copolymers for Self‐Healing Physically Crosslinked Hydrogels

The preparation of physically crosslinked hydrogels from quasi ABA‐triblock copolymers with a water‐soluble middle block and hydrophobic end groups is reported. The hydrophilic monomer N‐acryloylmorpholine is copolymerized with hydrophobic isobornyl acrylate via a one‐pot sequential monomer addition through reversible addition fragmentation chain‐transfer (RAFT) polymerization in an automated parallel synthesizer, allowing systematic variation of polymer chain length and hydrophobic–hydrophilic ratio. Hydrophobic interactions between the outer blocks cause them to phase‐separate into larger hydrophobic domains in water, forming physical crosslinks between the polymers. The resulting hydrogels are studied using rheology and their self‐healing ability after large strain damage is shown.

     

Synthesis and asymmetric anionic polymerization of substituted 7‐aryl‐2,6‐dimethyl‐1,4‐benzoquinone methides

Substituted 7‐aryl‐2,6‐dimethyl‐1,4‐benzoquinone methides which have an electron‐donating methoxy substituent at the para‐position (p‐OMe, 2a ) or an electron‐withdrawing chloro one at the para‐ (p‐Cl, 2b ), meta‐ (m‐Cl, 2c ) , and ortho‐positions (o‐Cl, 2d ) of the benzene ring were synthesized, and their asymmetric anionic polymerizations using the complex of lithium 4‐isopropylphenoxide with (?)‐sparteine were carried out in toluene at 0 °C. The polymers with negative specific rotation were obtained for all of four monomers, and the polymer obtained from 2a showed smaller specific rotation value than that of polymer having no substituent (p‐H, 1 ) on the phenyl group and the polymers obtained from 2b–d showed larger ones. It was found that the kind of a substituent and its substitution position on the phenyl group affect significantly the optical activity of polymers. The largest specific rotation value of [α]₄₃₅= ?153.2° was obtained in the polymerization of 2d with an ortho‐chloro substituent. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 437–444     

Synthesis of Well‐Defined Rod‐Coil‐Rod Polyhexylisocyanate‐block‐polystyrene‐block‐polyhexylisocyanate via One‐Pot Anionic Polymerization

A rod‐coil‐rod block copolymer, polyhexylisocyanate‐block‐polystyrene‐block‐polyhexylisocyanate, of controlled molecular weight was synthesized quantitatively via living anionic polymerization using potassium naphthalenide in the presence of sodium tetraphenylborate. The use of K⁺ as the counterion for the polymerization of styrene, and Na⁺ (NaBPh₄) for the polymerization of isocyanate leads to the formation of a well‐controlled novel triblock copolymer.

     

Synthesis and polymerization of 5‐(methacrylamido)tetrazole,a water‐soluble acidic monomer

The reaction of methacryloyl chloride with 5‐aminotetrazole gave the polymerizable methacrylamide derivative 5‐(methacrylamido)tetrazole ( 4 ) in one step. The monomer had an acidic tetrazole group with a pK_a value of 4.50 ± 0.01 in water methanol (2:1). Radical polymerization proceeded smoothly in dimethyl formamide or, after the conversion of monomer 4 into sodium salt 4‐Na , even in water. A superabsorbent polymer gel was obtained by the copolymerization of 4‐Na and 0.08 mol % N,N′‐methylenebisacrylamide. Its water absorbency was about 200 g of water/g of polymer, although the extractable sol content of the gel turned out to be high. The consumption of 4‐Na and acrylamide (as a model compound for the crosslinker) during a radical polymerization at 57 °C in D₂O was followed by ¹H NMR spectroscopy. Fitting the changes in the monomer concentration to the integrated form of the copolymerization equation gave the reactivity ratios r _4‐Na = 1.10 ± 0.05 and r_acrylamide = 0.45 ± 0.02, which did not differ much from those of an ideal copolymerization. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4333–4343, 2002     

Synthesis of 2‐Aminothiazole Derivatives in Easy Two‐Step,One‐Pot Reaction

Condensation of brominated ethyl acetoacetate with thiourea gives 2‐amino‐5‐ethoxycarbonyl‐4‐methylthiazole ( 1 ) and ethyl α‐(2‐amino‐4‐thiazolyl)acetate ( 2 ), indicating that bromination of the substrate occurs on both sides of the carbonyl group. X‐ray diffraction studies indicate weak hydrogen bonds of the amino groups, which are not observed in the IR spectra. The 1 molecule adopts planar S,O‐anti conformation in the crystal lattice, whereas the methylene group, insulating thiazole ring and the ester group in 2 molecule, makes it more flexible and makes the ester group nearly perpendicular to the thiazole ring. The small deviations of the bond lengths and angles indicate mesomeric interaction between complementary substituents across the thiazole ring.     

Polyester from dimethylketene and acetaldehyde: Direct copolymerization and β‐lactone ring‐opening polymerization

Two ways to obtain aliphatic polyesters (PEs) from dimethylketene and acetaldehyde were investigated. On the one hand, a direct anionic copolymerization was carried out in toluene at ?60 °C. The resulting polymer was mainly composed of PE units. On the other hand, a two‐step process involving the synthesis of 3,3,4‐trimethyl‐2‐oxetanone by [2+2] cycloaddition, followed by its ring‐opening polymerization, with various initiators and solvents, led to the expected PE. Molecular weights up to 9000 g mol^?1 (measured by nuclear magnetic resonance (NMR)), with narrow polydispersity around 1.2, were obtained. These polymers were found stable up to 274 °C under nitrogen and a broad and complex endothermic peak attributed to crystallinity was observed near 139 °C by differential scanning calorimetry (DSC). The crystallinity, measured by X‐ray diffraction, was close to 0.45. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

2,2,6,6‐Tetramethylpiperydinyl‐1‐oxyl (TEMPO) Functionalized Benzoxazines Prepared with a One‐Pot Synthesis for Reactive/Crosslinkable Initiators of Nitroxide Mediated Polymerization

In this work, the incorporation of a 2,2,6,6‐tetramethylpiperydinyl‐1‐oxyl (TEMPO) group to a benzoxazine ring is performed using a one‐pot synthesis for the preparation of TEMPO‐functionalized benzoxazine compounds and polymers as reactive and crosslinkable initiators for nitroxide‐mediated polymerization (NMP). The TEMPO‐functionalization reaction of benzoxazine, traced with ¹H NMR, is conducted with sequential radical transfer and coupling reactions. Moreover, polystyrene‐grafted polybenzoxazine copolymers are prepared with the TEMPO‐benzoxazine initiator and NMP of styrene. The polymerization system exhibits the characteristics of controlled radical polymerization, including controlled molecular weights of products and ability for sequential polymerization. Moreover, based on the chemical reactivity and crosslinking ability of benzoxazine groups, the synthesis route developed in this work will widen the scope of the design and synthesis of functional and high‐performance polymers.

     

Iron‐Promoted Practical One‐Pot Synthesis of 2,5‐Disubstituted Oxazoles

A practical one‐pot protocol for the synthesis of 2,5‐disubstituted oxazoles from 1‐aryl‐2‐nitroethanones was reported. In the presence of iron/AcOH in acetonitrile, the reaction of 1‐aryl‐2‐nitroethanones with trimethyl orthoacetate or trimethyl orthobenzoate delivered the corresponding 2,5‐disubstituted oxazoles in moderate to good yields.     

One‐Pot Catalytic Enantioselective Synthesis of 2‐Pyrazolines

A scalable, one‐pot, enantioselective catalytic synthesis of 2‐pyrazolines from beta‐substituted enones and hydrazines is described. Pivoting on a two‐stage catalytic Michael addition/condensation strategy, the use of an aldehyde to generate a suitable hydrazone derivative of the hydrazine was found to be key for curtailing background reactivity and tuning the catalyst‐controlled enantioselectivity. The new synthetic method is easy to perform, uses a new and readily prepared cinchona‐derived bifunctional catalyst, is broad in scope, and tolerates a range of functionalities with high enantioselectivity (up to >99:1 e.r.). The significant scalability of this methodology was demonstrated with the synthesis of more than 80 grams of a pyrazoline product with 89 % catalyst recovery.     

Facile One‐Pot Three‐Component Synthesis of Functionalized Pyridylfuran‐2‐amines

The reactive 1 : 1 zwitterionic intermediates generated in situ from the reaction between a series of isocyanides and diaroylacetylenes were trapped by pyridine carbaldehydes to yield highly functionalized 5‐pyridylfuran‐2‐amines in good yields (82–93%).     

Synthesis and characterization of novel nano size electroactive poly 4,4′‐diaminodiphenyl sulphone

The modification of electrodeposited polyaniline film by subsequent electrodeposition of 4,4′‐diaminodiphenyl sulfone (DDS) leads to a new material having nanostructure. The coated polymer films were treated with various pH solutions. The film adherent characteristics and surface morphology were studied using SEM. The electrochemically synthesized polyDDS revealed good redox behavior. The DDS was also polymerized by the chemical oxidation method using potassium persulphate. The polymer was characterized by UV‐Vis and FTIR spectral studies. The formation of polymer through the N? H group was understood from the single N? H stretching vibrational frequency at 3459 cm^?1. The X‐ray diffraction studies revealed the formation of nano sized (28 nm) crystalline polymer. The conductivity of the polymer was determined to be 1.07 × 10^?4 S.cm^?1. The solubility of the chemically polymerized powder was ascertained, and polyDDS showed good solubility in DMF and DMSO. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1702–1707, 2005