Synthesis of Diverse Asymmetric α,ω‐Dienes Via the Passerini Three‐Component Reaction for Head‐to‐Tail ADMET Polymerization

The Passerini three‐component reaction is applied to synthesize, in a one‐step procedure, diverse asymmetric α,ω‐dienes containing an acrylate and a terminal olefin. Such monomers are well known to undergo head‐to‐tail acyclic diene metathesis (ADMET) polymerization due to the high cross‐metathesis selectivity between acrylates and terminal olefins. Additionally, amphiphilic block copolymers are synthesized using a monofunctional PEG₄₈₀ monoacrylate, which acts as a selective chain‐transfer agent during the polymerization process. Thus, control over the molecular weight of the amphiphilic ADMET polymers is shown by using different ratios of mono­mer and chain‐transfer agent. All the polymers are thoroughly characterized, and their ability to form nanoparticles in aqueous solution is studied.

     

Synthesis of (Bio)‐Degradable Poly(β‐thioester)s via Amine Catalyzed Thiol−Ene Click Polymerization

The well‐known thiol‐ene click reaction is used to polymerize dithiols and diacrylate monomers. Using catalytic amounts of hexylamine, poly(ester‐sulfide)s are synthesized via consecutive Michael additions between 1,4‐butanedithiol and 1,6‐hexanediol diacrylate. The molecular weight of the polymers is controlled by the stoichiometric balance of the reagents and by optimizing reaction time. Maximum conversion is achieved at close to 20 min at room temperature. Thermal characterization of the polymer shows a melting temperature of 53 °C and good thermal stability of up to 200 °C. The poly(β‐thioester) readily degrades when in contact with acetic acid or NaOH solutions, but also degradation under more biological relevant conditions is indicated by partial hydrolysis of the ester linkages in phosphate buffers.     

Peroxide‐Grafted PDMS: Hydrosilylation Reaction and Thiol‐Ene Chemistry as an Alternative Pathway

Peroxide‐containing PDMS was synthesized according to a new pathway. Although hydrosilylation is one of the main reactions carried out in silicone chemistry, the catalysts used are very sensitive to the chemical nature of the reactants and remained inefficient to graft allylic peroxide. Radical catalyzed thiol‐ene chemistry was involved for the first time to yield an initiator group containing polymer. The peroxide‐grafted polysiloxane structure and decomposition were characterized using ¹H, ¹³C and ²⁹Si NMR, FT‐IR and Raman spectroscopies, SEC and DSC. These macroinitiators can be used to obtain polysiloxane able to undergo crosslinking.

     

Fatty Acid–Derived Aliphatic Long Chain Polyethers by a Combination of Catalytic Ester Reduction and ADMET or Thiol‐Ene Polymerization

Aliphatic long‐chain polyesters are a common class of renewable polymers and can be obtained by various synthetic routes, most notably from renewable fatty acids. In contrast, for aliphatic long chain polyethers only a few examples are known. Recently, the GaBr₃‐catalyzed reduction of esters to ethers has been introduced as convenient post‐polymerization modification to obtain polyethers directly from polyesters. Here, this reduction is applied to synthesize fatty acid–based ω,ω′‐unsaturated diene diether monomers, which are polymerized afterward by thiol‐ene or acyclic diene metathesis (ADMET) polymerizations in the “green” solvents methyl‐THF (2‐methyltetrahydrofuran) and polarclean. After polymerization, the thiol‐ene or ADMET polymers are modified by either oxidation or hydrogenation, respectively.     

Anionic Hybrid Copolymerization via Concurrent Oxa‐Michael Addition and Ring‐Opening Polymerizations

Here, a new type of anionic hybrid copolymerization is exploited via the concurrent oxa‐Michael addition of ethylene glycol and neopentyl glycol diacrylate and the ring‐opening polymerization of ε‐caprolactone. The hybrid copolymerization process and the resulting copolymers are characterized using nuclear magnetic resonance, size exclusion chromatography, differential scanning calorimetry measurements, and thermogravimetric analysis. The results show that the hybrid copolymerization can proceed smoothly under mild reaction conditions and that the synthesized copolymer contains ester and ether structures in the backbone, possibly endowing the polymers with good hydrophilicity and degradability. More importantly, the composition of the synthesized polymer can be easily adjusted by changing the monomer feed ratio, and the chain crystallization is significantly reduced due to the random copolymeric structure. This hybrid copolymerization reaction provides a new method for synthesizing degradable functional copolymers from commercially available materials. Hence, this polymerization is important not only in polymer chemistry but also in environmental and biomedical engineering.     

Controlled Thiol‐Ene Functionalization of Polyferrocenylsilane‐block‐Polyvinylsiloxane Copolymers

A general route for the controlled functionalization of polyferrocenylsilane‐block‐polyvinylsiloxane copolymers, which should be transferable to other silicone‐based materials, is developed utilizing the photoinitiated thiol‐ene reaction. Poly(ferrocenyldimethylsilane)₅₄‐block‐poly(methylvinylsiloxane)₅₁₀ (PFDMS₅₄‐b‐PMVS₅₁₀) is synthesized via sequential living anionic polymerization and quantitatively functionalized with a range of thiols, with the aim of tuning the solubility of the resulting materials for self‐assembly studies or incorporating more complex functionality for subsequent applications. When functionalization is attempted using a deficit of thiol, the photoinitiator 2,2‐dimethoxy‐2‐phenylacetophenone, used to accelerate the radical reaction, is found to cause significant cross‐linking of the polysiloxane chain. Reproducible percentage thiol‐ene functionalization of the polysiloxane block can be achieved by the use of PFDMS₅₃‐b‐PMVS₅₈/PDMS₄₄₄ (PDMS = polydimethylsiloxane), prepared by the copolymerization of cyclic siloxane monomers, [Me(CH?CH₂)SiO]₃ and [Me₂SiO]₃, to tune the vinyl group incorporation pre‐functionalization.

     

Synthesize Hyperbranched Polymers Carrying Two Reactive Handles via CuAAC Reaction and Thiol–Ene Chemistry

Structurally defined hyperbranched polymers (HBPs) bearing multiple azido peripheral groups and alkene dangling groups are constructed using the authors' recently developed chain‐growth copper‐catalyzed azide‐alkyne cycloaddition polymerization (CuAACP) of an alkene‐containing AB₂ monomer. Sequential integration of CuAAC and photo‐initiated thiol–ene reactions proves highly efficient and chemo‐selective functionalization of polymers at different placements with quantitative yield of both reactive groups. A variety of HBPs carrying both surface and internal functionalities are then produced, achieving quantitative/ratiometric incorporations of guest molecules in most cases. To demonstrate possible conjugation with bioactive ingredients, well‐defined HBPs decorated with peripheral cysteine moieties are produced as an example, showing pH responsiveness in water.     

Heterofunctionalized Multiarm Star Polymers via Sequential Thiol‐para‐Fluoro and Thiol‐Ene Double “Click” Reactions

The successful postfunctionalization of multiarm star polystyrene (PS) with pentafluorophenyl and allyl moieties at the periphery is demonstrated employing modular thiol‐para‐fluoro and photoinduced radical thiol‐ene double “click” reactions, respectively. α‐Fluoro and α‐allyl functionalized PS (α‐fluoro‐PS and α‐allyl‐PS) are in situ prepared by atom transfer radical polymerization of styrene and their mixture is used as macroinitiator in a crosslinking reaction with divinyl benzene (DVB) yielding (fluoro‐PS)_m–polyDVB–(allyl‐PS)_m multiarm star polymer. It is found that the multiarm star polymer includes nearly identical number of arms possessing pentafluorophenyl and allyl moieties at the periphery. The obtained multiarm star polymer is then reacted with 1‐propanethiol through thiol‐para‐fluoro “click” reaction to give (propyl‐PS)_m–polyDVB–(allyl‐PS)_m multiarm star polymer, which is subsequently reacted with N‐acetyl‐l ‐cysteine methyl ester via radical thiol‐ene “click” reaction in order to give well‐defined heterofunctionalized (propyl‐PS)_m–polyDVB–(cysteine‐PS)_m multiarm star polymer, with higher molecular weight and narrow molecular weight distribution. Multiarm star polymers are characterized by using viscotek triple detection gel permeation chromatography, ¹H, and ¹⁹F NMR.

     

Synthesis of Novel (bis-)1,5-Disubstituted-1H-tetrazole-Decorated Monomers and Their Respective Polymers via Thiol-ene Polymerization

Over the years, nitrogen-rich functional groups like tetrazole and its derivatives have received increasing interest in the chemistry of small molecules. There is a continuously growing interest in polymers decorated with nitrogen for potential biomedical applications because of their broad range of biological properties, such as being antibacterial, anticarcinogenic, and anti-inflammatory. On this premise, a new synthesis route is reported for nitrogen-decorated polymers via the combination of Ugi-azide four-multicomponent reaction (UA-4MCR) and thiol-ene polymerization. Accordingly, α,ω-diene monomers decorated with (bis-)1,5-disubstituted-1H-tetrazoles ( bis-1,5-DS-Ts ) are synthesized by using the UA-4MCR. Subsequently, the light-induced thiol-ene polymerization facilitates the efficient synthesis of novel tetrazole-decorated polymers with apparent number average molecular mass (M_n) up to 62 000 g mol⁻¹, which are characterized for their chemical, thermal, and optical properties. The comprehensive characterization of the synthesized polymers is paving the way toward a wealth of opportunities, ranging from biomaterials to energy storage−relevant materials.     

Cross‐Linked Nano‐Objects Containing Aldehyde Groups: Synthesis via RAFT Dispersion Polymerization and Application

Pure cross‐linked spherical micelles, nanowires, and vesicles are successfully fabricated from poly(2‐hydroxypropyl methacrylate‐b‐p‐(methacryloxyethoxy)benzaldehyde)s (PHPMA–b–PMAEBAs) through reversible addition‐fragmentation chain transfer dispersion polymerization of MAEBA in methanol using PHPMA as a macro‐CTA and subsequent cross‐linking. The cross‐linking reaction is conducted by stirring a mixture of 1,4‐butanediamine and the resultant nano‐objects in methanol at room temperature. For all polymerizations with feed molar ratios of MAEBA/PHPMA ranging from 75/1 to 240/1, the monomer MAEBA conversions are almost complete, and block copolymers with controlled molecular weight are obtained. The transmission electron microscopy, dynamic light scattering, and gel permeation chromatography results reveal that the following three factors significantly influence the morphology of the nano‐objects: the feed molar ratio of MAEBA/PHPMA, the copolymer concentration, and the degree of polymerization of PHPMA. The cross‐linked nano‐objects are very stable in good solvents, the spheres and nanowires slightly decrease in size after cross‐linking, whereas the vesicles slightly increase in size. The cross‐linked nano‐objects are stable in neutral solutions, but they dissociate in weekly acidic solutions. The loading of 1‐pyrenemethylamine (PMA) into the vesicles and the unloading of PMA from the vesicles are studied.

     

High Refractive Index Hyperbranched Polymers Prepared by Two Naphthalene‐Bearing Monomers via Thiol‐Yne Reaction

High refractive index (HRI) materials play an important role in optic‐electronic devices. In this study, two compounds with high content of naphthalene groups, 1,5‐dithiolnaphthalene and 1,3,5‐tris(naphthalyl–ethylnyl) benzene, are selected as “A₂” and “B₃” monomers, respectively to prepare hyperbranched HRI polymers. Metal‐free radical‐initiated “A₂ + B₃” thiol‐yne polyaddition is conducted successfully at different monomer molar ratios even for those sterically demanding molecules being able to adjust the molar mass as well as RI. Polymers with refractive index up to 1.79 at 589.7 nm are obtained, which are among the highest RI values so far reported for pure polymer‐based materials. The high RI, based on the high molar refraction of naphthalene group, metal‐free and easy one‐pot synthesis, high transparency in the visible area, good thermal stability, good solubility, and easy processability into thin films, make these polymers excellent candidates for optic‐electronic applications.

     

A Novel Synthetic Method for Well‐Defined Polymers Containing Benzotriazole and Diazobenzene Chromophores

PBHEMA was prepared by RAFT polymerization in the presence of CPDN and AIBN. Diazobenzene groups were introduced into the sidechains by post‐azo‐functionalization. The resulting polymers containing benzotriazol and azobenzene groups exhibited higher molecular weight than original polymers, narrow MWD ( = 1.17–1.26) and adjustable degrees of functionality. Thermal stabilities and glass transition temperatures of the polymers increased with the introduction of diazo chromophores. The molecular weight of the polymer had a slight effect on the T_g of the polymer. The polymer showed partial crystallization as the diazo content increased above 36%.

     

Microwave Assisted Synthesis of Thiol Modified Polymethacrylic acid and Its Cross‐Linking with Allyl Modified Polymethacrylic acid via Thiol‐ene “Click” Reaction

In this paper, we describe the thiol‐ene “click” reaction with modified poly methacrylic acid in water. The thiol group was implemented by a polymer analogous condensation reaction of polymethacrylic acid ( 1 ) and cysteamine ( 2 ), which was carried out in bulk by use of microwave. The allyl modified polymethacrylic acid ( 5 ) was obtained by DCC‐coupling of the allyl amine onto the polymethacrylic acid backbone. By combination of cysteamine ( 3 ) and allyl modified polymethacrylic acid ( 5 ) the thiol‐ene click reaction could be started with a redox initiator in aqueous solution at room temperature. The kinetics of this reaction were determined by ¹H NMR spectroscopy and the resulting hydrogels were analyzed by rheological measurements and differential scanning calorimetry (DSC).

     

Green Synthesis of a Bio‐Based Epoxy Curing Agent from Isosorbide in Aqueous Condition and Shape Memory Properties Investigation of the Cured Resin

The bio‐based diamine and epoxy monomer derived from isosorbide are synthesized. Especially, the diamine is obtained using microwave assistant thiol‐ene coupling reaction in the aqueous media and the influence of reaction parameters, such as initiator content and reaction time, are investigated. After curing the synthesized epoxy monomer together with the diamine, properties of the cured resins are studied by differential sscanning calorimetry, dynamic mechanical analysis, and thermogravimetric analyzer. Results demonstrate that the cured resin has good shape fixity, good shape recovery, and satisfied thermal stability despite the presence of heteroatoms. This bio‐based epoxy resin shows great potential to be used as a candidate for shape memory material. Considering the bio‐based feedstock and environmental friendly synthetic process, a “green + green” strategy to prepare thermosetting resins with advanced properties is provided in this paper.

     

New Second‐Order Nonlinear Optical Polymers Derived from AB2 and AB Monomers via Sonogashira Coupling Reaction

In this paper, a facile route was designed to prepare a new AB₂‐type polymer P1 via simple Sonogashira coupling reaction, also its corresponding linear analog ( P2 ) was obtained from AB monomer for comparison. Despite the relatively lower loading density of the effective chromophore moieties, P1 demonstrated higher second‐harmonic coefficient (153.9 pm · V^?1) than that of P2 (98.2 pm · V^?1), due to the three‐dimensional spatial isolation effect of the hyperbranched structure. The good results of P2 also indicated that the ladder shape may help to solve the problem existing in main‐chain polymers, the low poling efficiency.

     

The Renaissance of Side‐Chain Ferrocene‐Containing Polymers: Scope and Limitations of Vinylferrocene and Ferrocenyl Methacrylates

The synthesis of metal‐containing polymers and block copolymers has led to a rapidly expanding field of research interest for manifold potential applications. Within this contribution, some recent advances in the field of side‐chain ferrocene‐containing polymers focusing on poly(vinylferrocene) and poly(ferrocenyl methacrylates) are presented. The synthetic developments shown focus on living and controlled polymerizations, as well as surface‐initiated polymerization strategies. First attempts and recent developments for these novel redox‐responsive materials toward feasible applications are addressed.

     

Solid‐State Olefin Metathesis: ADMET of Rigid‐Rod Polymers and Ring‐Closing Metathesis

Summary: Solid‐state olefin metathesis of rigid‐rod acyclic diene metathesis (ADMET) polymers and ring‐closing metathesis (RCM) have been investigated. 1,4‐Dipropoxy‐2,5‐divinylbenzene ( 4 ) was synthesized and used in a bulk ADMET polymerization to produce oligomers of dialkoxy poly(phenylene vinylene). The reaction was continued in the solid state, effectively doubling the molecular weight. Solid‐state RCM was investigated with a variety of solid dienes and metathesis catalysts, and demonstrated in low conversions using amide diene 5 with catalysts 9 , 13 , and 14 .

     

New Functional Block Copolymers via RAFT Polymerization and Polymer‐Analogous Reaction

The synthesis of block copolymers consisting of nonfunctional and reactive blocks is reported. The precursor polymers are ABA triblock copolymers, consisting of S/VBC or MMA/GMA and prepared via RAFT polymerization. The reactive blocks are converted into blocks with new functionalities that are hard to achieve by direct polymerization. The new polymers are either amphiphilic, with acidic or basic blocks on the outside and a nonfunctional core, or have functionalities that are useful for further reactions like thiol‐ene or alkyne‐azide click reactions. Reaction success and degree of functionalization are determined via FTIR, elemental analysis, and MALDI‐TOF MS. The stability of the RAFT functionalities during the modification reactions is analyzed.     

Synthesis of Branched Polymers by Means of Living Anionic Polymerization, 9. Radical Coupling Reaction of 1,1‐Diphenylethylene‐Functionalized Polymers with Potassium Naphthalenide and Its Application to Syntheses of In‐Chain‐Functionalized Polymers and Star‐Branched Polymers

Radical coupling reactions of both 1,1‐diphenylethylene (DPE)‐chain‐end‐ and DPE‐in‐chain‐functionalized polymers with potassium naphthalenide have been studied under the conditions mainly in THF at –78°C. Chain‐end‐functionalized polymers having M̄_n values of less than 10 kg/mol were very efficiently coupled in more than 90% yield to afford the polymeric dianion that were dimeric coupled products with two 1,1‐diphenylalkyl anions in the middle of the chains. However, the dimer yield decreased with increasing the molecular weight. The dimer was obtained in 59% yield with use of the chain‐end‐functionalized polymer having M̄_n of 33.9 kg/mol. Well‐defined in‐chain‐functionalized polymers with two benzyl bromide and DPE moieties each have been successfully synthesized by the reaction of the polymeric dianion thus obtained with 1‐(4‐bromobutyl)‐4‐(tert‐butyldimethylsilyloxymethyl)benzene and 1‐[4‐(4‐bromobutyl)phenyl]‐1‐phenylethylene, respectively. The radical coupling reaction of in‐chain‐functionalized polymers with DPE (M̄_n ca. 20 kg/mol) with potassium naphthalenide also proceeded efficiently to afford the coupled products that were A₂A′₂ and A₂B₂ four‐arm star‐branched polymers with well‐defined structures (M̄_n ca. 40 kg/mol).     

Pyrene Containing Polymers for the Non‐Covalent Functionalization of Carbon Nanotubes

Pyrene containing diblock copolymers based on poly(methyl methacrylate) were synthesized and investigated regarding their adsorption on carbon nanotubes (CNT). The pyrene units were introduced using a reactive ester monomer for the build up of the second block which later on was reacted polymer‐analogously with amine functionalized pyrene derivatives. As we started from the same reactive ester intermediate, full block length identity is given. We varied the length of the anchor block to find an optimal block length and used pyren‐1‐yl‐methylamine as well as 4‐pyren‐1‐yl‐butylamine as anchor units. For both anchor units a maximal adsorption was found for 13 and 20 anchor units, respectively. The absolute adsorption was best for the 4‐pyren‐1‐yl‐butylamine anchor units as the longer spacer enhances the mobility of the anchor unit. The dispersion diagram of CNTs and diblock copolymer in terms of dispersion stability was investigated and a stable dispersion of 2.5 mg · ml^?1 CNTs in THF was found.