Aqueous RAFT Polymerization of Acrylamide and N,N‐Dimethylacrylamide at Room Temperature

Summary: The first example of a room temperature reversible addition‐fragmentation chain transfer polymerization conducted directly in aqueous media is detailed. Under these conditions acrylamide and N,N‐dimethylacrylamide may be polymerized in a controlled fashion to near quantitative conversions employing a difunctional trithiocarbonate chain transfer agent (CTA). Hydrolysis studies conducted at pH 5.5 suggest that the CTA is stable up to approximately 50 °C.

     

Synthesis and Self‐Assembly of Amphiphilic Diblock Copolymers using a Fluorescently Labeled N‐Alkoxyamine Initiator

Summary: An initiator for nitroxide mediated ‘living’ free radical polymerization was prepared with a fluorescent tag attached to the initiating alkyl radical terminus. This was used to synthesize amphiphilic poly(acrylic acid)‐block‐polystyrene diblock copolymers, which self assembled in a tetrahydrofuran/buffer solution to form structures that are visible by fluorescence.

     

A New Type of Thermoresponsive Copolymer with UCST‐Type Transitions in Water: Poly(N‐vinylimidazole‐co‐1‐vinyl‐2‐(hydroxymethyl)imidazole)

1‐Vinyl‐2‐(hydroxymethyl)imidazole ( 2 ) is synthesized by a procedure described in the literature. Corresponding copolymers with upper critical solution temperature (UCST)‐type transitions in water and high‐glass transition temperatures (T_g) are prepared by free radical copolymerization with N‐vinylimidazole ( 1 ). Depending on the copolymer composition, the cloud point can be varied between 19 and 41 °C. As the copolymer composition is identical with the monomer feed ratio, the cloud point can be easily tuned in the desired range. Furthermore, a distinctive pH‐dependence and salt effect can be observed.

     

Low‐Temperature Growth of Thick Polystyrene Brushes via ATRP

Summary: This contribution describes the graft polymerization of polystyrene (PS) by atom transfer radical polymerization at 50, 60, and 75 °C. Thick PS brushes were grown from initiator‐functionalized PGMA layers on silicon, and constant growth rates provide indirect evidence that the polymerizations were controlled.

Formation of polystyrene brushes at T < T_g by ATRP of styrene from α‐bromoester initiator‐functionalized poly(glycidyl methacrylate) layers.     

Microwave Accelerated Synthesis of N‐Phenylmaleimide in a Single Step and Polymerization in Bulk

Summary: This paper reports the microwave mediated direct synthesis of N‐phenylmaleimide ( 3 ) from maleic anhydride ( 1 ) and aniline ( 2 ) by using microwave irradiation. Good yields and very short reaction times were the main aspects of the method. The reaction conditions and kinetics of this process were investigated. Microwave irradiation in a boiling solvent showed the existence of a significant specific microwave effect. The microwave homopolymerization of 3 in bulk using 2,2′‐azoisobutyronitrile (AIBN) as a free radical initiator was also carried out.

Kinetic curves for the synthesis of N‐phenylmaleimide in a MW and in an oil bath at 144 °C (boiling xylene).     

Preparation of Polystyrene Particles by Dispersion Polymerization in an Ionic Liquid

Submicron‐sized monodisperse polystyrene (PS) particles were successfully prepared by dispersion polymerization of styrene in an ionic liquid, N,N‐diethyl‐N‐methyl‐N‐(2‐methoxyethyl)ammonium bis(trifluoromethanesulfonyl)imide ([DEME][TFSI]) at 70 °C with poly(vinyl pyrrolidone) (PVP) as a stabilizer. At the optimum PVP and styrene concentrations with regard to preparation of stable polymer particles, the number‐average diameter and coefficient of variation were 350 nm and 5.7%, respectively. The particle size increased with a decrease in the PVP concentration and an increase in the styrene concentration. Moreover, we succeeded in producing PS particles by thermal polymerization in the absence of a radical initiator at 130 °C in [DEME][TFSI] using a conventional reactor (not autoclave) utilizing the advantages of non‐volatility and thermal stability of the ionic liquid.

     

Living Anionic Polymerization of tert‐Butyl Acrylate in a Flow Microreactor System and Its Applications to the Synthesis of Block Copolymers

Living anionic polymerization of tert‐butyl acrylate initiated by 1,1‐diphenylhexyllithium is conducted in a flow microreactor system in the presence of lithium chloride. A high degree of control over the molecular weight distribution is achieved under easily accessible conditions, for example at ?20 °C. The subsequent reaction of a reactive polymer chain end with an alkyl methacrylate in an integrated flow micoreactor system leads to the formation of a block copolymer with a narrow molecular weight distribution.

     

Fabrication of Micropatterned Gold Nanoparticle Arrays as a Template for Surface‐Initiated Polymerization of Stimuli‐Responsive Polymers

Summary: This paper demonstrates a new, reliable, and simple method for fabricating micropatterned nanoparticle arrays that can serve as templates for the surface‐initiated polymerization of polymer brushes. As a proof of concept, we micropatterned gold nanoparticles (Au‐NPs, ≈10 nm) onto glass, silicon, polystyrene, and gold surfaces by a simple three‐step process: (1) microcontact printing of soluble polymer, (2) incubation with a solution of Au‐NPs, and (3) lift‐off of the template in a mixture of ethanol and deionized water. 40 µm wide features were successfully fabricated without any significant defects or nonspecific adsorption on the background. To demonstrate the utility of these Au‐NP templates, we subsequently polymerized N‐isopropylacrylamide by surface‐initiated polymerization, using a surface‐bound initiator.

Synthesis of PNIPAAm brushes from micropatterned Au‐NP.     

Access to Poly{N‐[3‐(dimethylamino)propyl](meth)acrylamide} via Microwave‐Assisted Synthesis and Control of LCST‐Behavior in Water

In the present paper, the microwave (MW)‐assisted synthesis of the alkaline N‐[3‐(dimethylamino)propyl]methacrylamide ( 4 ) and ‐acrylamide ( 5 ) monomers within minutes is described. The reaction was carried out by mixing and subsequent irradiation of 3‐dimethylamino‐1‐propylamine ( 3 ) and (meth)acrylic acid ( 1 / 2 ) without addition of solvent. After polymerization, the obtained homopolymers ( 6 / 7 ) exhibit lower critical solution temperature (LCST) behavior in water at 35 °C only at pH = 14. The LCST‐behavior can be influenced by N‐oxidation of the tertiary amino group with hydrogen peroxide or by formation of a polymer‐inclusion complex ( 6a ) of 6 and β‐cyclodextrin (β‐CD) by addition of randomly‐methylated β‐CD.

     

Preparation of Well‐Defined PVOH/C60 Nanohybrids by Cobalt‐Mediated Radical Polymerization of Vinyl Acetate

Summary: Poly(vinyl acetate) chains end‐capped by a Co(acac)₂ complex [PVAc‐Co(acac)₂] were prepared by bulk cobalt‐mediated radical polymerization (CMRP) of vinyl acetate and used for grafting fullerene (C60) with four PVAc arms at low temperature (30 °C). A photoactive water‐soluble poly(vinyl alcohol)/C60 nanohybrid was then prepared by hydrolysis of the PVAc arms of the nanohybrid. Because of photoactivity and very low cytotoxicity, this type of water‐soluble nanohybrid is very promising for the photodynamic cancer therapy.

Strategy for the preparation of PVAc/C60 nanohybrid and hydrolysis of PVAc/C60 nanohybrid into PVOH/C60 nanohybrid.     

A New Crystal Form,Polymorphism, and Multi‐Morphology in Biodegradable Poly(3‐hydroxypropionate)

Summary: A new crystal morphology (δ form) of poly(3‐hydroxypropionate) (PHP) is found in cast and melt‐crystallized PHPs with low molecular weight, in which the PHP chains possibly adopt a 2₁ helix rather than the trans conformation found in the β or γ form. The fusion temperature‐ and the crystallization temperature‐dependent polymorphism are responsible for the dual morphologies and the unique growth kinetics of spherulites in the melt‐crystallized PHPs.

a) A dual‐morphology developed at 70 °C in PHP films after melting at 117 °C and b) that formed during cooling at a rate of 1 °C · min⁻¹ from 130 °C.     

Ethylene Polymerization Catalyzed by Titanium(IV) Complexes of a Triaryloxoamine Ligand [TiX{(OArCH2)3N}]

Summary: Titanium complexes containing a triaryloxoamine ligand, [TiX{(O‐2,4‐R₂C₆H₂‐6‐CH₂)₃N}] (R = Me, tBu; X = OiPr, O‐2,6‐iPr₂C₆H₃), exhibited notable catalytic activity for ethylene polymerization in the presence of MAO, especially at temperatures between 100 and 120 °C. Their activity increased upon the addition of a small amount of AlMe₃.

     

Synthesis of Well‐Defined Telechelic Aromatic Polyamides by Chain‐Growth Polycondensation: Application to the Synthesis of Block Copolymers of Polyamide and Poly(tetrahydrofuran)

Well‐defined telechelic‐type aromatic polyamides having a secondary amino group and a phenyl ester moiety at each chain end were prepared by the chain‐growth polycondensation of phenyl 4‐(octylamino)benzoate ( 1 ) with initiator 2 (N‐tert‐butoxycarbonylated 1 ), followed by deprotection of the N‐protecting group of the initiator unit. This polycondensation was applied to the synthesis of well‐defined di‐ and triblock copolymers of aromatic polyamides and poly(tetrahydrofuran) (poly(THF)) by the reaction of the terminal secondary amino group of the polyamide with the living cationic propagating group of poly(THF).

Block copolymers of polyamide and poly(tetrahydrofuran).     

Nitroxide‐Mediated Radical Dispersion Polymerization of Styrene in Supercritical Carbon Dioxide Using a Poly(dimethylsiloxane‐block‐styrene) Alkoxyamine as Initiator and Stabilizer

Summary: Nitroxide‐mediated dispersion polymerization of styrene in supercritical carbon dioxide has been performed successfully at 110 °C using a new polymeric so‐called inistab species, which fulfils the dual functions of an initiator and a colloidal stabilizer. The inistab species comprised a poly(dimethylsiloxane) block and a polystyrene block end‐capped with the nitroxide N‐tert‐N‐butyl‐N‐[1‐diethylphosphono‐(2,2‐dimethylpropyl)] nitroxide (SG1). The dispersion polymerization resulted in sub‐micron sized polymer particles and polymers of narrow polydispersity.

TEM micrograph of PS particles prepared in the dispersion polymerization of S in scCO₂ in the presence of PDMS(\overline M _{\rm n} = 6 500)‐b‐PS(\overline M _{\rm n} = 4 500)‐SG1 at 110 °C.     

Synthesis of Block Copolymers Modified with Phosphonate Ester Groups Using Nitroxide‐Mediated Radical Polymerization

Summary: Phosphonate groups were introduced into block copolymers of styrene derivatives either as single end‐groups or as small blocks using nitroxide‐mediated radical polymerization. In order to combine the hydrophobic and hydrophilic segments, block copolymers with N,N‐dimethyl acrylamide were synthesized. After hydrolysis to phosphonic acid groups, adsorption of the polymer onto metal oxides was possible.

Conversion of the phosphonate groups by transesterification with trimethylbromosilane (TMBS), followed by hydrolysis of the silylester group.     

Acid‐Degradable Core‐Crosslinked Micelles Prepared from Thermosensitive Glycopolymers Synthesized via RAFT Polymerization

A thermoresponsive block copolymer, namely poly(acryloyl glucosamine)‐block‐poly(N‐isopropylacryamide) (PAGA₁₈₀‐b‐PNIPAAM₃₅₀) was simultaneously self‐assembled and crosslinked in aqueous medium via RAFT polymerization at 60 °C to afford core‐crosslinked micelles exhibiting a glycopolymer corona and a PNIPAAM stimuli‐responsive core. An acid‐labile crosslinking agent, 3,9‐divinyl‐2,4,8,10‐tetraoxaspiro[5.5]undecane, was employed to generate thermosensitive and acid‐degradable core‐shell nanoparticles. Stable against degradation at pH = 6 and 8.2, the resulting core crosslinked micelles readily hydrolyzed into well‐defined free block copolymers at lower pH (30 min and 12 h respectively at pH = 2 and 4).

     

Design and Synthesis of Fast‐Degrading Poly(anhydride‐esters)

Fast‐degrading, salicylate‐based poly(anhydride‐esters) were designed to degrade and release the active component, salicylic acid (SA), within 1 week. The polymer degradation was enhanced by using shorter or oxygen‐containing aliphatic chains. A copolymer of diglycolic acid was also made with a salicylate‐based diacid for comparison of polymer properties, including SA release. Both methods resulted in polyanhydrides with molecular weights ranging from 14 500 to 27 800 Da and displayed glass transition temperatures near physiological conditions, namely 33–40 °C. The homo‐ and copolymers completely degraded within one week releasing the chemically incorporated SA.

     

Synthesis of Oligosaccharide‐Branched Ribofuranan by Ring‐Opening Polymerization of a New Anhydroribo Trisaccharide Monomer

A new anhydroribotrisaccharide monomer, A2B3LR ( 1 ), was synthesized and ROP was carried out to elucidate the polymerizability and to obtain oligosaccharide‐branched polysaccharides with defined structures. The new trisaccharide monomer was found to be polymerized readily with BF₃ · OEt₂ as a catalyst at ?40 °C to give a lactose‐branched polymer. Copolymerization with ADBR gave the corresponding copolymers in good yields. After removal of protective benzyl groups, D ‐lactose‐branched ribofuranans with free hydroxyl groups were obtained in good yields. The structure of polymers was analyzed by ¹H, ¹³C, and two‐dimensional NMR measurements, suggesting that D ‐lactose‐branched ribofuranans had (1 → 5)‐α stereoregularity.

     

Porous Protein‐Based Nanoparticle Hydrogel for Protein Chips with Improved Sensitivity

We have discovered a novel method to prepare a protein‐based hydrogel, that is, a ‘three‐dimensional nanostructured protein hydrogel’ (3D NPH), which is composed of loosely inter‐connected protein–polymer hybrid nanoparticles. The 3D NPH can be easily prepared by spotting a protein/polymer mixture on a substrate. Surprisingly, gold nanoparticles carrying protein molecules easily diffuse into the 3D NPH through pores and spaces. We have shown that the protein chip made by our 3D NPH method has tremendously improved sensitivity in detecting protein–protein interactions compared with that by direct protein immobilization methods.