Combining Step-Growth and Chain-Growth Polymerizations in One Pot: Light-Induced Fabrication of Conductive Nanoporous PEDOT-PCL Scaffold.

A novel method based on light-induced fabrication of a poly (3,4-ethylenedioxythiophene)-polycaprolactone (PEDOT-PCL) scaffold using phenacyl bromide (PAB) as a single-component photoinitiator is presented. HBr released from the step-growth polymerization of EDOT is utilized as an in situ catalyst for the chain-growth polymerization of ε-caprolactone. Detailed investigations disclose the formation of a self-assembled nanoporous electroconductive scaffold (1.2 mS cm-1 ). Fluorescence emission spectra of the fabricated scaffold exhibit a mixed solvatochromic behavior, indicating specific interactions between the self-assembled scaffold and solvents with varying polarities, as evidenced by transmission electron microscopy (TEM). Moreover, the same light-induced technique can also be applied for bulk photopolymerization showcasing the versatility and wide-ranging scope of the originated method. In brief, this study introduces a novel approach for light-induced polymerization reactions that is merging step-growth and chain-growth mechanisms. This innovative approach is promising to facilitate in situ polymerization of monomers possessing diverse functionalities.

Exploiting Visible-Light Induced Radical to Cation Transformation Pathway for Reactivity Enhanced Electrophilic Aromatic Substitution Polymerization of Heteroaromatics.

A straightforward approach is employed to synthesize methylene-bridged poly(hetero aromatic)s based on furan, pyrrole, thiophene, and thiophene derivatives. The process involves an electrophilic aromatic substitution reaction facilitated by a visible light-initiated system consisting of manganese decacarbonyl and an iodonium salt. The approach mainly relies on the formation of halomethylium cation, the attack of this cation to heteroaromatic, regeneration of methylium cation on the heteroaromatic, and reactivity differences between halomethylium and heteroaromatic methylium cations for successful polymerizations. This innovative synthetic strategy lead to the formation of polymers with relatively high molecular weights as the stoichiometric imbalance between the comonomers increased. Accordingly, these newly obtained polymers exhibit remarkable fluorescence properties, even at excitation wavelengths as low as 330 nm. Moreover, by harnessing the halogens at chain ends of homopolymers, block copolymers are successfully synthesized, offering opportunities for tailored applications in diverse fields.

Visible-Light-Induced Cationic Polymerization of Isobutylene: A Route toward the Synthesis of End-Functional Polyisobutylene.

The visible-light-induced cationic polymerization of isobutylene with a dimanganese decacarbonyl (Mn2(CO)10)/diphenyl iodonium hexafluorophosphate (Ph2I+PF6-) photoinitiating system in a CH2Cl2/n-hexane mixture at -30 °C was reported. It was shown that polymerization is initiated by chloromethylisobutyl carbocations generated by the oxidation of chloromethylisobutyl radicals by Ph2I+PF6-. The latter are formed via chlorine abstraction from solvent (CH2Cl2) by MnCO5· radicals, which are generated by the photoinduced decomposition of Mn2(CO)10, followed by single isobutylene addition. This initiating system allowed us to synthesize valuable low molecular weight polyisobutylene with a relatively low polydispersity (Mn = 2000-3000 g mol-1; D < 1.7) and high content of exo-olefin end groups (up to 90%). The molecular weight of polyisobutylenes could be easily controlled in the range from 2000 to 12000 g mol-1 by changing the diphenyl iodonium salt concentration. Poly(ß-pinene) with Mn = 5000 g mol-1 and D ∼ 2.0 was successfully synthesized using the same photoinitiating system.

One-Pot Synthesis of Amide-Functional Main-Chain Polybenzoxazine Precursors.

Main-chain polybenzoxazines containing amide linkages were successfully prepared in one pot. Three different polymers were synthesized by reacting 3,4-dihydrocoumarine (DHC) and paraformaldehyde with 1,3-diaminopropane or 1,6-diaminohexane or Jeffamine ED-900. The one-pot reaction proceeded through the combination of the ring-opening of DHC with amines, and subsequent Mannich and ring-closure reactions occurring in a cascading manner. The obtained polymer from Jeffamine exhibited good film-forming properties, and free-standing flexible films were easily solvent- casted on Teflon plates. All polymeric precursors were characterized by spectroscopic analysis, and their curing behavior and thermal stability were investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA).

Ring-Opening Polymerization of 1,3-Benzoxazines via Borane Catalyst.

Tris(pentafluorophenyl)borane was used as Lewis acid catalyst to lower the ring opening polymerization temperature (ROP) of 1,3-benzoxazines. Dynamic scanning calorimeter studies revealed that on-set ROP temperatures were decreased as much as 98 °C for model benzoxazine compounds. Catalytic polymerization was traced by both FTIR and ¹H NMR, and revealed that tris(pentafluorophenyl)borane acted rapidly and fast curing achieved. Moreover, thermal properties of resulting polybenzoxazines were investigated by thermogravimetric analysis (TGA) and found out that the catalyst has high impact on char yield and even 3 mol % catalyst augmented char yields up to 13%.

Recycling and Self-Healing of Polybenzoxazines with Dynamic Sulfide Linkages.

In this work, a recycling and self-healing strategy for polybenzoxazines through both S-S bond cleavage-reformation reaction and supramolecular attractions is described. Both recyclable and self-healable polybenzoxazines can be prepared from low cost chemicals with a simple procedure in only 30 minutes. For this purpose, inverse vulcanization of poly(propylene oxide)benzoxazine (PPOB) and diallybenzoxazine (B-al) with elemental sulfur was performed at 185 °C. The obtained cross-linked polymer films exhibited thermally driven recycling ability up to 5 cycles. Moreover, the self-healing ability of a test specimen was shown. Spectral characterizations, thermal stability and fracture toughness of the films were investigated after each recycling.

Polybenzoxazine: a powerful tool for removal of mercury salts from water.

A reusable macroporous polybenzoxazine resin with high specific surface area was prepared as sorbent material for the removal of mercury salts. For this purpose, allyl-functionalized bis-benzoxazine was cured in dimethyl sulfoxide by thermally activated ring-opening polymerization at 180 °C for 3 d followed by a freeze-drying process. The porous structure of the resin was confirmed by SEM analysis and N2 adsorption/desorption studies at 77.3 K. Among various metal ions, namely, Pb(II), Fe(II), Mn(II), Cu(II), Zn(II), and Cd(II), the porous polybenzoxazine resin exhibited a specific sorption behaviour towards Hg(II). Mainly chemisorption and to some extent adsorption mechanisms were proposed for the observed high loading capacity of the resin. As evidenced by FTIR spectral analysis, the chemisorption is attributed to the coordination system formed between free OH and tertiary amino groups in the polybenzoxazine structure and Hg(II) ions. It was also demonstrated that the porous polybenzoxazine can be regenerated simply by treatment with acids. The resin was recycled for up to seven cycles without any significant loss of activity, as proved by sorption and desorption experiments.

Versatile Postmodification of Conjugated Microporous Polymers Using Thiol-yne Chemistry.

Radical thiol-yne chemistry is used for the modification of microporous networks with aliphatic alcohols. The degree of functionalization can be tuned by varying the reacted amount of thiol. Porosity analysis indicates that the microporosity can be preserved within a certain range, however, a decrease in pore size is observed.

Mesoporous Graphitic Carbon Nitride as a Heterogeneous Visible Light Photoinitiator for Radical Polymerization.

The use mesoporous graphitic carbon nitride (mpg-C3N4) in conjunction with tertiary amines as initiators in visible-light-induced free radical polymerization is described. The initiation mechanism involves photoinduced free radical generation by scavenging holes with amines and subsequent hydrogen abstraction. The efficiency of the photoinitiation is controlled by the nature of the amines and specific surface area of the carbon nitride powder. Apparently, amines with higher basicity and available hydrogens provide more favorable conditions for the photoinitiation process. Due to its heterogeneous nature, the photoinitiator preserves its photoinitiation activity after the polymerization and can easily be separated and used for further polymerizations.

Synthesis and characterization of polyacetylene with side-chain thiophene functionality.

A new polyacetylene derivative with electroactive thiophene substituent, namely poly(2-methylbut-2-enyl thiophene-3-carboxylate) was synthesized and characterized. For this purpose, novel acetylene monomer was synthesized by the reaction of 3-thiophenecarboxylic acid with propargyl bromide and polymerized with a Rh catalyst to give the corresponding polymer. The chemical structure of the polymer was characterized to comprise the conjugated backbone and electroactive thiophene side group. UV spectral changes of the polymer with temperature were also studied. The polymer exhibited better thermal stability than the unsubstituted polyacetylenes.