Polymer Chemistry最新文献

This study explores a pioneering catalytic reaction to obtain functional polymers and valuable byproducts. Using RuCl₂(PPh₃)₃ as a catalyst activates the C–N and N–H bonds in aromatic diamines, when combined with 1,4-butynediol. This activation initiates de-ammonification polycondensation, resulting in aromatic polyamines with a pyrrolyl end group and ammonia as a byproduct. The ammonia generated during the polycondensation process can be captured in cold water. The generation of ammonia during polycondensation was confirmed by UV-vis spectroscopy using the Nessler's reagent method. Subsequently, the aromatic polyamines were further functionalised via polymer reactions with 1,4-butanesultone and butyl isocyanate in the NH group. This yielded products with pendant sodium N-butylsulfonate and N-butylamide groups, respectively. The former exhibited a single-ion conductivity. Potential reaction mechanisms involving Ru-catalysed N–H and C–N bond activation in AD, along with the formation of terminal pyrrolyl groups, were investigated using density functional theorycalculations and ²H NMR spectroscopy.

Many applications of polymer materials, such as adhesives, require a polymerization process at room temperature and ambient atmosphere. In those cases, two-component (2K) systems based on redox initiation truly stand out due to their reliable performance. Herein, we present a deep insight into the polymerization kinetics of a newly developed initiation system based on the copper catalyzed cleavage of diborane compounds, followed by rheology coupled with NIR. The analysis of different diboranes led us to further investigate the diborane concentration dependency and the effects on gel time that can be observed. Furthermore, it is shown that the diborane/Cu system yields polymers with high molecular weight at high double bond conversions. In addition, the perspectives of diborane/Cu initiation for radical polymerization are presented, as various different monomer classes showed excellent reactivity towards polymerization, enabling the great potential of this initiation system for various applications in polymer chemistry.

Based on DFT-level computational studies, ZnEt₂ was implemented as a chain transfer agent (CTA) to promote the coordinative chain transfer (co)polymerization of ethylene for the first time with a metallocene complex of Nd. The use of ZnEt₂ in combination with Mg(ⁿBu)_1.5(ⁿOct)_0.5 compared to the use of Mg(ⁿBu)_1.5(ⁿOct)_0.5 alone, improves several key aspects of the polymerization process. When ethylene is polymerized, an increase of catalytic activities is observed and narrower molar mass distributions are obtained due to reduced β-H transfer and faster reversible chain transfer reactions. In copolymerization of ethylene with butadiene, the presence of ZnEt₂ has no impact on the polymerization process in terms of polymerization kinetics and microstructure of the final copolymer. Nevertheless, it acts as an excellent CTA. Using ZnEt₂ in combination with MesMgBr rather than Mg(ⁿBu)_1.5(ⁿOct)_0.5 enables selective chain transfer between neodymium and zinc and promotes a nearly quantitative chain-end functionalization with acyl chloride.

Three polymerized small molecule acceptors (PSMAs), namely PY-TP, PY-TPMe2, and PY-TPMe4, were designed and synthesized by employing (bisthiophene)benzene linkers containing various methyl-substituted phenylene groups. All the PSMAs exhibit similar absorption maxima in films as well as LUMO energy levels. However, the increased number of methyl groups on the linkers induces steric hindrance and decreases the coplanarity of the polymer backbones, which, in turn, increases intermolecular π–π stacking distances. When the three acceptors are blended with a classical polymer donor PM6, PY-TPMe4 with a highly twisted backbone has a large π–π stacking distance and excessive phase separation, whereas PY-TP and PY-TPMe2 with moderately twisted backbones demonstrate more compact π–π stacking and suitable phase separation morphology. As a result, PY-TP and PY-TPMe2 exhibit better exciton dissociation and charge transport, leading to much higher photovoltaic performance compared to PY-TPMe4. Particularly, PY-TPMe2 effectively regulates the crystallinity and achieves a more suitable phase separation morphology in the blend films. The optimal PY-TPMe2-based photovoltaic device exhibits the best exciton dissociation and charge transport performance, achieving the highest power conversion efficiency (PCE) of 8.4% among the devices based on the three PSMAs, with a high open-circuit voltage (V_OC) of 0.97 V, a short-circuit current density (J_SC) of 14.74 mA cm⁻² and a fill factor (FF) of 59.65%. These findings provide new insights into the regulation of the molecular packing and photovoltaic performance of polymer acceptors through simple methylation modification on linkers for designing novel PSMA materials.

Chiral conjugated oligomers with circularly polarized luminescence (CPL) have received great interest and been extensively researched. However, chiral conjugated oligomers with donor–acceptor (D–A) structures are poorly developed. In this paper, a series of D–A-type chiral conjugated oligomers were synthesized by the copolymerization of axially chiral acceptors and achiral donors through Pd-catalyzed Buchwald–Hartwig C–N coupling reactions. The resulting chiral conjugated oligomers exhibit donor-dependent fluorescence in solution with emission wavelengths ranging from 500 to 574 nm and photoluminescence quantum yields (Φ_PL) of up to 49%, which can be attributed to the ICT transition derived from the D–A oligomer backbone. Obvious CPL response signals can be detected for the chiral conjugated oligomers with luminescence dissymmetry factors (g_lum) of up to 1.3 × 10⁻³, which can be tuned via the variation of achiral donors. This work can provide a novel strategy for the design of chiral conjugated polymers or oligomers with D–A structures and tunable CPL signals.

Well-defined star poly(substituted glycolide) (s-PSG) homopolymers with predetermined lengths and numbers of arms, which are alternatives to polylactides and polyglycolides, may offer great opportunity for the modulation of their physical properties, such as glass transition temperature (T_g), crystallinity, hydrophobicity, and surface characteristics due to their geometric and structural differences. Herein, we report the synthesis of s-PSG homopolymers, including a four-armed symmetrical poly(L-diisopropyl glycolide) (4s-PLDIPG) and poly(L-diisobutyl glycolide) (4s-PLDIBG) from the ring opening polymerization (ROP) of their monomers in the presence of tin(II) 2-ethylhexanoate [Sn(Oct)₂] as a catalyst and pentaerythritol as an initiator via a core-first approach under melt conditions. 4s-PLDIPG 8 exhibits lower T_g, melting temperature (T_m) and crystallinity % than 4s-PLDIPG 10 (T_g: 33.7 °C vs. 35.9 °C; T_m: 143.9 °C vs. 183.4 °C; X_c: 16.7% vs. 19.1%) due to its lower M_n per arm. 4s-PLDIPG 8 also has a dramatically lower T_m and crystallinity % than its linear counterpart PLDIPG 17 (T_m: 143.9 °C vs. 190.6 °C; X_c: 16.7% vs. 26.7%) due to its short arm length. As the side chain length of s-PSG homopolymers increased, there was a corresponding increase in the water contact angles and surface roughness values of the thin films, while the surface free energy decreased. This correlation between side chain length and surface properties was further validated by SEM and AFM profiles, which confirmed the impact of extended side chains on the polymer's surface characteristics.