Enzyme‐Catalyzed Preparation of Aliphatic Polyesters Containing Thioester Linkages

Aliphatic polyesters containing thioester linkages were enzymatically prepared by both the copolymerization of lactone with mercaptoalkanoic acid and by the transesterification of polyesters with mercaptoalkanoic acids. The enzymatic copolymerization of ε‐caprolactone with 11‐mercaptoundecanoic acid (11MU) and 3‐mercaptopropionic acid (3MP) was performed under reduced pressure using an immobilized lipase from Candida antarctica (CA). The transesterification of poly(ε‐caprolactone) and poly[(R)‐3‐hydroxybutyrate] was carried out with 11MU and 3MP using lipase CA under reduced pressure.

     

One‐Pot Difunctionalization of Poly(ω‐pentadecalactone) with Thiol‐Thiol or Thiol‐Acrylate Groups,Catalyzed by Candida antarctica Lipase B

Summary: An enzymatic one‐pot procedure has been developed for the synthesis of difunctional polyesters containing terminal thiols and acrylates. Candida antarctica lipase B was used as a catalyst for the ring‐opening polymerization of ω‐pentadecalactone. The polymerization was initiated with 6‐mercaptohexanol, then terminated with γ‐thiobutyrolactone or vinyl acrylate to create two types of difunctional polyesters with a very high content of thiol‐thiol or thiol‐acrylate end‐groups.

Difunctionalization of poly‐PDL.     

Effect of Comonomer‐Unit Compositional Distribution on Thermal and Crystallization Behavior of Bacterial Poly[(3‐hydroxybutyrate)‐co‐(3‐mercaptopropionate)]

The physical properties of novel sulfur‐containing biopolymers, poly[(3‐hydroxybutyrate)‐co‐(3‐mercaptopropionate)]s [P(3HB‐co‐3MP)s], have been investigated in detail by¹H and ¹³C NMR spectroscopy, wide‐angle X‐ray diffraction (WAXD) analysis, DSC, and FT‐IR spectroscopy. Based on a solvent/non‐solvent (chloroform/heptane) fractionation method, an original P(3HB‐co‐3MP) sample with 3MP unit content of 16.3 mol‐% was fractionated into eight fractions with 3MP unit content ranging from 10.3 to 37.2 mol‐% and number‐average molecular weight from 0.4 × 10⁵ to 2.9 × 10⁵. The thermal and crystallization behavior were found to be greatly affected by the comonomer‐unit composition and its distribution. Furthermore, the 3MP comonomer unit was found to be included in the crystalline phase in some fractions.

     

CF3SO3H Initiated Cationic Polymerization of Diisopropenylbenzenes in Macrobatch and Microflow Systems

CF₃SO₃H was found to serve as a more superior initiator for the polymerization of diisopropenylbenzenes than the conventionally used acids such as H₂SO₄. Much faster polymerization at lower temperatures seems to be ascribed to the higher acidity of CF₃SO₃H. The use of microflow systems was also found to be effective in increasing the indane unit content, especially for 1,4‐DPB. Fast mixing and uniformity of the temperature seem to be responsible. The thus‐obtained polymers of high indane unit content serve as useful materials having high thermal resistance and low dielectric constants.

     

Polybenzimidazoles for High Temperature Fuel Cell Applications

Summary: Fuel cells were designed for high temperature operations. Poly[2,2′‐(m‐phenylene)‐5,5′‐bibenzimidazole] (PBI) was synthesized in a solution of P₂O₅, CH₃SO₃H, and CF₃SO₃H. The PBI was dissolved in a mixture of CF₃CO₂H and H₃PO₄ and the solution was used for the preparation of Pt catalyst slurry for membrane electrode assembly. The single cell showed a current density of 280 mA · cm⁻² at a cell voltage of 0.5 V with feeds of H₂ and O₂ at 160 °C and without external humidification.

     

Discriminating Among Co‐monomer Sequence Distributions in Random Copolymers Using Interaction Chromatography

Interaction chromatography has been employed to validate that adsorption of poly[styrene‐co‐(4‐bromostyrene)] (PBr_xS) random copolymers, where x denotes the mole fraction of 4‐bromostyrene (4–BrS) in PBr_xS in solution depends on the average number of adsorptive segments, the type of adsorbing substrate, and on the co‐monomer sequence distribution in PBr_xS.

     

Fabrication of Metal‐Block‐Copolymer Composite Films by a Palladium‐Catalyzed Electroless Nickel‐Plating Process

Summary: Homogeneous films of PI‐b‐PDMAEMA are prepared on top of silicon (100) substrates. The free film surface shows microdomains of PDMAEMA within a PI matrix. These microdomains act as templates for the highly site‐selective synthesis of metal nanoparticles via palladium‐catalyzed electroless nickel plating. The particle formation is studied by atomic force microscopy in tapping mode and implications for a redox reaction and a nanoparticle growth mechanism on the surface of nanopatterned films are discussed.

Chemical structure of the PI‐b‐PDMAEMA copolymer and AFM phase image of a PI‐b‐PDMAEMA film on Si (100) substrate.     

Phase Behavior and Thermal Properties for Binary Blends of Bacterial Poly(3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate)s with Narrow‐Comonomer‐Unit Compositional Distribution

The miscibility and the effect of compositional distribution on physical properties were investigated for binary blends of biosynthesized poly(3‐hydroxybutyrate) [P(3HB)] and comonomer compositionally fractionated poly(3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate)s [P(3HB‐co‐3HH)] with narrow compositional distribution. Biosynthesized P(3HB‐co‐3HH) samples were compositionally fractionated using solvent (chloroform)/nonsolvent (n‐heptane) mixtures. The binary blends of fractionated P(3HB‐co‐3HH)s with different 3HH unit content were prepared by casting from solution in chloroform. The miscibility and the thermal properties of these blends were analyzed by differential scanning calorimetry (DSC). It was found that the two components are miscible in the amorphous phase when the difference in 3HH unit content between the two component polymers of these blends is less than 20 mol‐%, subsequently they are immiscible when the difference is larger than 30 mol‐%. By comparing the thermal properties of the binary blends of fractions, with those for the fractions themselves, and with those for the bacterially as‐produced unfractionated copolyesters, the effects of compositional distribution on the properties of copolyesters were discussed.

Glass transition temperatures of blends PHB/H10, H10/H20, and PHB/H20 versus total 3HH unit content in the blends. The solid lines are the best fits of the experimental results of the P(3HB‐co‐3HH) fractions with narrow compositional distribution.     

Encapsulation of a Single Metal Nanoparticle with Tunable Size in a Monodisperse Polymer Microcapsule

A versatile approach to fabricate monodisperse poly[styrene‐co‐(divinyl benzene)] (PS‐co‐DVB) microcapsules that contain a single gold nanoparticle (AuNP) has been demonstrated. Using the PS‐co‐DVB microcapsule as a microreactor, aqueous HAuCl₄ and NaBH₄ solutions are subsequently infiltrated. The size of the resulting AuNP inside of the PS‐co‐DVB microcapsules is easily tunable by controlling the repeated infiltration cycles of aqueous HAuCl₄ and NaBH₄. PS‐co‐DVB microcapsules that contain a single silver and palladium nanoparticle are also obtained by following a similar protocol.

     

Design of a Linear Poly(3‐hexylthiophene)/Fullerene‐Based Donor‐Acceptor Rod‐Coil Block Copolymer

Novel fullerene‐grafted poly(3‐hexylthiophene) (P3HT)‐based rod‐coil block copolymers have been synthesized. The regioregular P3HT rod block has been synthesized by a modified Grignard metathesis reaction (GRIM). An original in situ end‐capping reaction has been developed in order to convert the P3HT block into an efficient macro‐initiator for the nitroxide‐mediated radical polymerization (NMRP) of the coil block. Controlled radical polymerization of the second poly(butylacrylate‐stat‐chloromethylstyrene) [P(BA‐stat‐CMS)] block has been done through various conditions leading to different coil block lengths. The final electron donor‐acceptor block copolymer has been obtained after C₆₀ grafting in soft conditions. Copolymers have been characterized by ¹H NMR and size exclusion chromatography. Optical characterizations, before and after C₆₀ grafting, are reported.

     

New Strategy for Controlling Biodegradability of Biodegradable Polyesters by Enzyme‐Catalyzed Surface Grafting

A novel preparation method for the core‐shell type biodegradable polyesters or biodegradable materials grafted with biodegradable polyesters was developed by alkaline surface treatment of biodegradable polyester films and subsequent enzymatic polymerization of aliphatic lactones, one example of which is shown in this study, i.e., the preparation of poly(L ‐lactide) (PLLA) film grafted with poly(ε‐caprolactone). It is revealed that only alkaline surface treatment or the combination of alkaline surface treatment and enzyme‐catalyzed grafting, the former and the latter, respectively accelerating and delaying the enzymatic degradation of PLLA, will give PLLA materials having a wide variety of biodegradability. Also, the specificity of the enzyme used for hydrolysis could be used to confirm the grafted chain species.

     

Synthesis of Graft Bacterial Polyesters for Nanoparticles Preparation

Graft copolymers of bacterial polyesters were prepared by direct condensation of poly(3‐hydroxyoctanoate‐co‐9‐carboxy‐3‐hydroxydecanoate) (PHOD) and poly(ethylene glycol) (PEG) or poly(lactic acid) (PLA). Nanoparticles from PHO, PHOD, PHOD‐g‐PEG, and PHOD‐g‐PLA were obtained by solvent displacement without stabilizer, and their stability in different aqueous media with different salt concentrations were studied. The results showed that the presence of hydrophilic PEG on the particle surface prevents the aggregation promotion by salts in aqueous solution. PHOD‐g‐PEG appears to be a promising candidate for site‐specific drug delivery systems.

¹H NMR spectrum of PHOD‐g‐PLA in CDCl₃.     

Hydration Changes during Thermosensitive Association of a Block Copolymer Consisting of LCST and UCST Blocks

Summary: Thermosensitive association of a diblock copolymer consisting of poly(3‐dimethyl(methacryloyloxyethyl) ammonium propane sulfonate) (PdMMAEAPS), as an upper critical solution temperature (UCST) block, and poly(N,N‐diethylacrylamide) (PdEA), as a lower critical solution temperature (LCST) block, has been investigated by using IR spectroscopy. The ν(CO) and ν(SO) bands of the PdMMAEAPS block and the amide I band of PdEA block critically changed at the UCST and LCST, respectively, indicating that the segmental interaction of each block is altered at each transition.

The double temperature responsiveness of a UCST block and LCST block containing diblock copolymer. Micelles form at temperatures both below the UCST and above the LCST of the blocks.     

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.

     

A Strategy for Synthesis of Ion‐Bonded Supramolecular Star Polymers by Reversible Addition‐Fragmentation Chain Transfer (RAFT) Polymerization

We have developed a novel strategy for the preparation of ion‐bonded supramolecular star polymers by RAFT polymerization. An ion‐bonded star supramolecule with six functional groups was prepared from a triphenylene derivative containing tertiary amino groups and trithiocarbonate carboxylic acid, and used as the RAFT agent in polymerizations of tert‐butyl acrylate (tBA) and styrene (St). Molecular weights and structures of the polymers were characterized by ¹H NMR and GPC. The results show that the polymerization possesses the character of living free‐radical polymerization and the ion‐bonded supramolecular star polymers PSt, PtBA, and PSt‐b‐PtBA, with six well‐defined arms, were successfully synthesized.

     

Preparation of a Polyethylene Latex by Catalytic Hydrogenation of a Polybuta‐1,4‐diene‐Based Dispersion

Summary: Fully linear polyethylene‐based latexes have been prepared by the hydrogenation of polybuta‐1,4‐diene dispersions. The latter were synthesized via dispersion ring‐opening metathesis polymerization of cycloocta‐1,5‐diene, and hydrogenated using RuCl₂(PPh₃)₃ as catalyst, without any further treatment. A high hydrogenation efficiency was achieved as demonstrated by different techniques including DSC, and ¹H NMR and FT‐IR spectroscopy. The hydrogenation process could be carried out without detrimental effect on particle size and colloidal stability as evidenced by optical microscopy and light scattering analysis.

Optical microscopy photograph of a polybutadiene‐based dispersion after hydrogenation. No change in size is observed.     

From Polyesters to Polyamides Via O?N Acyl Migration: An Original Multi‐Transfer Reaction

A new strategy for the synthesis of polyamides from polyesters of hydroxyl‐containing amino acids using a multi O N acyl transfer reaction was developed. This original approach allowed the synthesis of three generations of polymers from the same starting monomer. The polymerization of N‐benzyloxycarbonyl‐serine and its γ‐homologated derivative provided the Z‐protected polyesters; then the water‐soluble polycationic polyesters were obtained by removal of the Z‐protecting group; and finally the polyamides were obtained by a base‐induced multi O N acyl transfer, both in aqueous or organic medium. The key step transfer reaction was monitored by the disappearance and appearance of characteristic NMR proton signals and IR bands of polyesters and polyamides.

     

A Cationic Water‐Soluble Poly(p‐phenylenevinylene) Derivative: Highly Sensitive Biosensor for Iron‐Sulfur Protein Detection

Summary: A new water‐soluble cationic ammonium‐functionalized poly(p‐phenylenevinylene) (PPV‐NEtMe) was successfully synthesized and exhibited high sensitivity (K_sv = 6.9 × 10⁷ M ⁻¹) on rubredoxin, a type of anionic iron‐sulfur (Fe‐S) proteins. Further investigation showed that the biosensitivity of the cationic conjugated polymer is strongly dependent on the nature of the buffer solution and the concentration of the conjugated polymer used in the analyses.

The schematic diagram of anionic rubredoxin detected by PPV‐NEtMe.     

Fabrication of Biomimetic Super‐Amphiphobic Surfaces Through Plasma Modification of Benzoxazine Films

Summary: In this study, a method for producing super‐amphiphobic surfaces through plasma modification of benzoxazine films is presented. Microroughening and fluorination of the benzoxazine films occurs during the plasma treatment process and a rugged surface with a micro/nano binary structure is formed. The combined effect of low surface energy and substrate roughness results in high advancing contact angles (157° for water, 152° for diiodomethane) and low contact angle hysteresis.

SEM image of a cross‐linked polybenzoxazine film treated with Ar plasma (7 min) heated to 200 °C (1 h) and treated with CF₄ plasma for 30 s.     

Electronic Properties and Field‐Effect Transistors of Thiophene‐Based Donor–Acceptor Conjugated Copolymers

Summary: The thiophene‐quinoxaline donor–acceptor conjugated copolymer poly[(thiophene‐2,5‐diyl‐alt‐(2,3‐diheptylquinoxaline‐5,8‐diyl)] (PTHQx) was explored as a semiconductor in thin‐film organic field‐effect transistors (OFETs). A hole mobility of 3.6 × 10⁻³ cm² · V⁻¹ · s⁻¹ and an on/off current ratio of 6 × 10⁵ were observed in p‐channel OFETs made from spin‐coated PTHQx thin films. The electronic structures of PTHQx and a related thiophene‐thienopyrazine donor–acceptor copolymer were calculated by density functional theory. Atomic force microscopy of PTHQx thin films showed a polycrystalline grain morphology that varied with the substrate.

Output (left) and transfer (right) characteristics of a PTHQx (structure shown) organic field‐effect transistor.