Types Of Diamines Research Articles

Enantioselective Transformations by "1 + x" Synergistic Catalysis with Chiral Primary Amines.

ConspectusSynergistic catalysis is a powerful tool that involves two or more distinctive catalytic systems to activate reaction partners simultaneously, thereby expanding the reactivity space of individual catalysis. As an established catalytic strategy, organocatalysis has found numerous applications in enantioselective transformations under rather mild conditions. Recently, the introduction of other catalytic systems has significantly expanded the reaction space of typical organocatalysis. In this regard, aminocatalysis is a prototypical example of synergistic catalysis. The combination of aminocatalyst and transition metal could be traced back to the early days of organocatalysis and has now been well explored as an enabling catalytic strategy. Particularly, the acid-base properties of aminocatalysis can be significantly expanded to include usually electrophiles generated in situ via metal-catalyzed cycles. Later on, aminocatalyst has also been exploited in synergistically combining with photochemical and electrochemical processes to facilitate redox transformations. However, synergistically combining one type of aminocatalyst with many different catalytic systems remains a great challenge. One of the most daunting challenges is the compatibility of aminocatalysts in coexistence with other catalytic species. As nucleophilic species, aminocatalysts may also bind with metal, which leads to mutual inhibition or even quenching of the individual catalytic activity. In addition, oxidative stability of aminocatalyst is also a non-neglectable issue, which causes difficulties in exploring oxidative enamine transformations.In 2007, we developed a vicinal diamine type of chiral primary aminocatalysts. This class of primary aminocatalysts was developed and evolved as functional and mechanistic mimics to the natural aldolase and has been widely applied in a number of enamine/iminium ion-based transformations. By following a "1 + x" synergistic strategy, the chiral primary amine catalysts were found to work synergistically or cooperatively with a number of transition metal catalysts, such as Pd, Rh, Ag, Co, and Cu, or other organocatalysts, such as B(C6F5)3, ketone, selenium, and iodide. Photocatalysis and electrochemical processes can also be incorporated to work together with the chiral primary amine catalysts. The 1 + x catalytic strategy enabled us to execute unexploited transformations by fine-tuning the acid-base and redox properties of the enamine intermediates and to achieve effective reaction and stereocontrol beyond the reach individually. During these efforts, an unprecedented excited-state chemistry of enamine was uncovered to make possible an effective deracemization process. In this Account, we describe our recent efforts since 2015 in exploring synergistic chiral primary amine catalysis, and the content is categorized according to the type of synergistic partner such that in each section the developed synergistic catalysis, reaction scopes, and mechanistic features are presented and discussed.

Crown Ether Copolymerized Polyimide Film: Enhanced Mechanical, Thermal Properties and Low Dielectric Constant under High Frequency.

Polymer materials with a low dielectric constant and low dielectric loss have the potential to be applied to high-frequency signal transmissions, such as mobile phone antennas and millimeter wave radars. Two types of diamines, 4,4'-diamino-p-tetraphenyl (DPT) and crown ether diamine (CED), were prepared for ternary copolymerization with BPDA in this study. Cross-links with molecular chains were formed, increasing molecular chain distance by utilizing rings of CED. The MPI films exhibit a good thermal performance with the increase in CED addition, with Tg > 380 °C and CTE from -4 × 10-6 K-1 to 5 × 10-6 K-1. The Young's modulus can reach 8.6 GPa, and the tensile strength is above 200 MPa when 5% and 7% CED are introduced. These MPI films exhibit good mechanical performances. The dielectric constant of PI-10% film can go as low as 3.17. Meanwhile, the relationship between dielectric properties and molecular structure has been demonstrated by Molecular Simulation (MS). PI molecules are separated by low dielectric groups, resulting in a decrease in the dielectric constant.

Enhancing gas separation performance of polyimide with Tröger’s bases: Unveiling the impact on polymer and carbon molecular sieve membranes

The potential of carbon molecular sieve membranes (CMSM) for gas separation is widely recognized, and the key precursor for these membranes is polyimide (PI). This study focuses on enhancing the gas separation properties of CMSMs by introducing a unique structural element, Tröger’s bases, into polyimides, resulting in the creation of five distinct polyimides containing Tröger’s bases (PI-TBs). The incorporation of Tröger’s bases has a profound impact on the arrangement of polymer chains within the PIs, leading to a substantial improvement in gas permeability without compromising selectivity. Following carbonization at 600 °C, the resultant CMSMs exhibit significantly enhanced gas permeability while preserving, and in some cases, improving gas selectivity. Among the various types of diamines considered, the 6FDA variant of PI-TB stands out, boasting outstanding gas permeability with a H2 permeability of 4991.0 Barrer and a H2/CH4 selectivity of 30.7; this level of performance surpasses the 2015 Robeson’s upper bound. Furthermore, thermal analysis coupled with mass spectrometry (TG-MS) reveals that the pyrolysis of Tröger’s bases commences prior to that of polyimide. This sequential degradation process facilitates the formation of pyridine N and promotes the π-stacking of PI chains; both of which are instrumental in maintaining excellent gas selectivity. These findings provide valuable insights into the roles of Tröger’s bases in enhancing the gas separation performance of PIs and CMSMs, offering a promising avenue for further advancements.

Recyclable and Degradable Vinylogous Urethane Epoxy Thermosets with Tunable Mechanical Properties from Isosorbide and Vanillic Acid

Conventional epoxy resins derived from unsustainable petroleum resources are unrecyclable and nondegradable. Herein, we facilely synthesized biobased vinylogous urethane epoxy thermosets (VUEs) using sustainable isosorbide and vanillic acid via a post-crosslinking method. Isosorbide was directly functionalized to isosorbide-bis-acetoacetate, which could be reacted with primary amines provided by triethylenetetramine and diamine to generate linear prepolymers with vinylogous urethane bonds. Then, VUEs were constructed, in which permanent covalent crosslinkers were generated by ring opening of the epoxy group in vanillin acid with the secondary amine already present in the linear prepolymer. By integrating different types of diamines, the obtained biobased VUEs display tunable mechanical properties; specifically, the tensile strength varies from 31.5 to 114.6 MPa and the elongation at break ranges from 9.5 to 150.0%. The VUE using ethylenediamine (TT-VUE) is comparable to that of bisphenol-A epoxy in terms of its mechanical qualities. The incorporation of vinylogous urethane bonds confers recyclable capability on VUEs, and the recycled VUEs show a lap shear strength of 7.39 MPa, indicating their potential application in adhesives. We envisaged that biobased VUEs with desirable tunable mechanical properties would be excellent replacements for petroleum-based epoxy resins.

Preparation and enhanced flame retardancy of co‐polybenzoxazines containing diacetal structure

AbstractA comparative study on the flame retardancy of two polybenzoxazines with and without a diacetal structure, p(A) and p(B), is firstly carried out by microscale combustion calorimeter (MCC). It is proved that the presence of the diacetal structure can endow p(A) with good flame retardancy with a low heat release capacity (HRC). Then, the monomer of this diacetal containing p(A), A‐boz, is used to modify a typical diamine type benzoxazine (M‐boz) to improve its flame retardancy. The effects of A‐boz with different ratios on curing behavior, heat resistance and thermal stability of the co‐polybenzoxazines of M‐boz and A‐boz, p(M/A)s, are analyzed by differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy, dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA). Furthermore, the flame retardancy of p(M/A)s is investigated by UL‐94 test, limiting oxygen index (LOI) and MCC, and the degradation and flame retardant mechanisms are investigated by scanning electronic microscopy (SEM), Raman spectra and TGA‐FTIR. When the addition amount of A is 20 wt%, the LOI value of p(M/A) is as high as 39.5% and its flame retardant rating reaches UL‐94 V‐0. In addition, the mechanical properties of p(M/A)s are tested. The results suggest that the Tg and char yield at 800°C in N2 of p(M/A)s increase from 210 to 243°C and 45% to 51%, respectively. This work suggests that the incorporation of the diacetal structure is an effective strategy to improve the flame retardancy of resins.

Polybenzoxazine/carbon nanotube nanocomposites as a polymeric sensing material for volatile organic compounds

The emissions of volatile organic compounds (VOCs) have hazardous effects on humans and the environment, and hence they should be detected and reduced. In this study, polybenzoxazine (PBZ) and amine-functionalized multiwall carbon nanotube (MWCNT) composites were synthesized as a sensor for VOCs. MWCNT were functionalized with two types of diamines, namely, 1,6-hexanediamine (HDA) and phenylenediamine (PDA). HDA or PDA treated MWCNTs were loaded into the benzoxazine matrix with different weight percentages (0.1, 0.3, 0.5, and 1%). FTIR analysis confirmed the chemical attachment of the two types of diamines on MWCNT. XRD diffraction and scanning electron microscopy (SEM) were used to investigate the nanofillers morphology and clarify the differences between pristine and amine-functionalized MWCNT. Thermal gravimetric analysis (TGA) was used to study the composites’ thermal stability and degradation behavior. It was found that, in contrast to neat PBZ, the major degradation temperature of PBZ/0.5%MWCNT-PDA nanocomposites were enhanced by 10%. The electrical conductivity of PBZ was 6.32 × 10–9, which was enhanced to 6.11 × 10–7 in the composites with 1% MWCNT-PDA. This material was tested as a VOCs sensor for methanol, acetone, and toluene and showed that PBZ/1% MWCNT-PDA composite responded to all the vapors.

Surface Modification of Matrimid® 5218 Polyimide Membrane with Fluorine-Containing Diamines for Efficient Gas Separation.

Polyimide membranes have been widely investigated in gas separation applications due to their high separation abilities, excellent processability, relatively low cost, and stabilities. Unfortunately, it is extremely challenging to simultaneously achieve both improved gas permeability and selectivity due to the trade-off relationship in common polymer membranes. Diamine modification is a simple strategy to tune the separation performance of polyimide membranes, but an excessive loss in permeability is also generally observed. In the present work, we reported the effects of diamine type (i.e., non-fluorinated and fluorinated) on the physicochemical properties and the corresponding separation performance of a modified membrane using a commercial Matrimid® 5218 polyimide. Detailed spectroscopic, thermal, and surface analyses reveal that the bulky fluorine groups are responsible for the balanced chain packing modes in the resulting Matrimid membranes compared to the non-fluorinated diamines. Consequently, the modified Matrimid membranes using fluorinated diamines exhibit both higher gas permeability and selectivity than those of pristine Matrimid, making them especially effective for improving the separation performance towards H2/CH4 and CO2/CH4 pairs. The results indicate that the use of fluorinated modifiers may offer new opportunities to tune the gas transport properties of polyimide membranes.

Novel polyimide in presence of benzoxazole: Synthesis and characterization

Dianhydride (3′, 4, 4′-biphenyltetracarboxylic dianhydride (BPDA) and Diamine (p-phenylediamine (PDA) in a ratio of 1:1 polymerize Polyimide (PI) in N-Methyl-2-Pyrrolidone (NMP) as solvent. A series of PI films were made in presence of BPDA and two types of Diamines (PDA and HAB (4, 4′-Diamino-3, 3′-dihydroxybiphenyl) where Diamines ratios were 95:5, 90:10, 80:20, 50:50, 0:100. HAB was introduced as source of benzoxazole. Fourier transform infrared (FTIR) confirmed that there was benzoxazole ring in polyimide after curing. FTIR, Differential scanning calorimetry (DSC), UV-spectrophotometer, Scanning electronic microscope (SEM), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA) and stress-strain tests were used to measure the performance of the films. The results indicated that small content of benzoxazole (5%) increase thermal stability, glass transition temperature and tensile strength prominently than the pristine PI which may use for microelectronics.

Effect of Alkyl Structures on the Anti‐stacking and Anchoring of Pd/Diamine‐Functionalized Graphene Nanoparticles in Application in Suzuki Reaction

Main observation and conclusionThree diamines (1,8‐diaminooctane/p‐phenylenediamine/biphenylenediamine) with different alkyl groups were used to synthesize the functionalized graphene networks. Pd as the common metal catalyst was used to explore the effects of alkyl types of diamines on anti‐stacking, metal anchoring ability of functional graphene and hence the catalytic performance. The results were discussed by characterization of the material and its catalytic properties. All catalysts showed excellent catalytic performance on the Suzuki cross‐coupling reaction with a high yield of up to 100%. The p‐phenylenediamine and biphenylenediamine functionalized graphene with larger specific surface area was beneficial to improve the stability of the graphene catalyst and maintain good catalytic activity after 5 cycles. The Pd nanoparticles in 1,8‐octanediamine materials have smaller size and a smaller loading with the same or even better catalytic performance than p‐phenylenediamine, biphenylenediamine materials, due to the stronger electron donating ability of N of octanediamine than that of p‐phenylenediamine.

Oligomeric ricinoleic acid synthesis with a recyclable catalyst and application to preparing non-isocyanate polyhydroxyurethane

As a consequence of the great demand and extended application of polyurethanes in various fields, the development of green processes for their production and functional polyurethane materials has received widespread attention. In this regard, the biomass-derived polyurethane via the non-isocyanate route could be promising. In this work, the castor-based polyurethanes were designed and synthesized through a non-isocyanate route by employing ricinoleic acid as the starting material, in which the oligomeric ricinoleic acid (ORA) with variable average polymerization degree was used as the key intermediate. To access the ORA with different average polymerization degree, the solid Lewis acid tin(II) oxide (SnO) was developed as the efficient and recyclable catalyst and the average polymerization degree of ORA was regulated by the reaction time at 210 °C. After sequential esterification, epoxidation, cycloaddition with CO2 and polyaddition with 1,6-hexamethylene diamine (HMDA) or isophorone diamine (IPDA), a series of polyhydroxyurethanes (PHUs) with different tensile strength and elongation at break as well as the thermal stability and the glass transition temperature were obtained depending on the type of diamine and the average polymerization degree of ORA, indicating the functional role of the polymerization degree of ORA in regulating the mechanical and thermal properties of the resulting materials. This protocol for the castor-based PHUs preparation in this work not only represents a green and sustainable way to produce bio-based material, but also provides a convenient way to change the average polymerization degree of ORA and then alter the properties of resulting polyurethanes.

Facile Fabrication of Mechanically Strong and Thermal Resistant Polyimide Aerogels with an Excess of Cross-Linker

ABSTRACT In this study, we report the effect of the number of formulated repeat units (n), the type of diamine and the cross-linker content on pore morphology, structure and mechanical properties of vacuum-dried polyimide aerogels. Morphology observations demonstrate that an excess of cross-linker is conducive to increase the pore size, strengthen and stiffen the network to avoid the collapse and suppress the irreversible shrinkage during the vacuum drying procedure. For 2,2'-dimethylbenzidine derived aerogels, the pore diameter increases with increasing cross-linker content or decreasing n. The shrinkage is higher in aerogels derived from 4,4'-oxidianiline due to the chain rigidity and mobility difference compared to rigid diamine-based aerogels, resulting in lower porosity and higher density. Compared with those previously reported aerogels with the same backbone chemistries, vacuum dried polyimide aerogels herein show higher compressive strength and Young’s modulus resulting from higher density and coarser skeleton networks. More importantly, isothermal aging results reveal very low increasement of shrinkage and density occurring over the aging period, which even can be ignored. The facile, low-cost vacuum drying procedure, dramatically improved mechanical properties, and superior thermal resistance will broaden the practical applications of polyimide aerogels.

The study on curing and weight-loss mechanisms of benzoxazine during thermal curing process

Based on the weight loss and small molecule volatiles released during the thermal curing process of three kinds of benzoxazines, bisphenol A/aniline type benzoxazine (BA-a), p-cresol/diamine type benzoxazine (MPH-mda) and 2,4-xylenol/4,4′-methylenebis-(2,6-diisopropyl) aniline type benzoxazine (DMPH-mdpa), their curing mechanisms and the weight-loss mechanisms were studied. The weight-loss ratios and structure changes of these benzoxazines during the curing process were studied by weighing method, Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). The volatiles released from these benzoxazines during different curing stages were collected by a self-made experimental device. The structures of these volatiles were characterized by FTIR and proton nuclear magnetic resonance spectroscopy (1H NMR). The results showed that the mixtures of imine, triazine, aniline and Schiff base were released from the cracking of the intermediate during the thermal curing of BA-a. Compared with BA-a, the weight loss of MPH-mda was smaller, and its volatile was a small amount of stable diamine type Schiff base. For DMPH-mdpa, because all active reaction points on benzene ring were occupied by alkyl groups, it cannot form effective polymer structures after ring-opening reactions, which led to that DMPH-mdpa had the most weight loss during the curing process, and mainly generated phenol type volatiles.

Transparent Polyimide/Organoclay Nanocomposite Films Containing Different Diamine Monomers.

Poly (amic acid) s (PAAs) were synthesized using 4,4′-(hexafluoroisopropyl-idene) diphthalic anhydride (6FDA) and two types of diamines—bis(3-aminophenyl) sulfone (BAS) and bis(3-amino-4-hydroxyphenyl) sulfone (BAS-OH). Two series of transparent polyimide (PI) hybrid films were synthesized by solution intercalation polymerization and thermal imidization using various concentrations (from 0 to 1 wt%) of organically modified clay Cloisite 30B in PAA solution. The thermo-mechanical properties, morphology, and optical transparency of the hybrid films were observed. The transmission electronic microscopy (TEM) results showed that some of the clays were agglomerated, but most of them showed dispersed nanoscale clay. The effects of -OH groups on the properties of the two PI hybrids synthesized using BAS and BAS-OH monomers were compared. The BAS PI hybrids were superior to the BAS-OH PI hybrids in terms of thermal stability and optical transparency, but the BAS-OH PI hybrids exhibited higher glass transition temperatures (Tg) and mechanical properties. Analysis of the thermal properties and tensile strength showed that the highest critical concentration of organoclay was 0.50 wt%.

Design and application of polyurea microcapsules containing herbicide (oxyfluorfen)

ABSTRACT Polyurea, a controlled release material, has been widely applied in agricultural fields due to high thermal stability and low cost. In this article oxyfluorfen polyurea microcapsules suspension was successfully prepared by interfacial polymerization using diisocyanate and polyamines such as Ethylenediamine, Hexamethylenediamine, Diethylenetriamine in presence of green solvent, i.e., N,N-dimethyldecanamide. The microcapsule suspension of oxyfluorfen has not been researched yet by using solvent N,N-dimethyldecanamide and polyamines. The effect and the type of diamines on the morphology and properties of the microcapsules have been investigated. The synthesized microcapsules were characterized by scanning electron microscope, ultraviolet spectrometry, Fourier transform iInfrared spectrometer, thermogravimetric analysis and particle size analyser. The effect of the core to shell ratio on encapsulation efficiency and release kinetics were also studied. The oxyfluorfen microcapsules had an excellent encapsulation efficiency (98.2%) using EDA as the monomer and Release kinetics depended upon the type of monomers used and also on core to shell ratio used (6.5:1, 5:1, 4:1). As core to shell ratio was increased the encapsulation efficiency was found to decrease. Prepared Microcapsules when sprayed on paddy crop was found to be safe in comparison with Emulsifiable concentrate sample.

Preparation and properties of benzoxazine blends with intumescent flame retardancy

A benzoxazine containing both alkynyl and aldehyde groups (PHB-apa) was used to modify typical diamine type benzoxazine (PH-ddm) with different ratios to get good flame retardancy. The effects of PHB-apa on curing reaction behavior, heat resistance and thermal stability of the copolymers of PHB-apa and PH-ddm, poly(PH/PHB)s, were analyzed by DSC, DMA and TGA, respectively. The flame retardancy of poly(PH/PHB)s was investigated by vertical combustion test, limiting oxygen index (LOI) and cone calorimeter. The results suggested that the flame retardancy of PH-ddm was greatly improved by adding a small amount of PHB-apa. When the addition amount of PHB-apa was only 1:12 (the molar ratio of PHB-apa to PH-ddm), the LOI value of poly(PH/PHB-12) was as high as 33.8 and UL-94 test was improved from V-1 to V-0 rating. Moreover, the structures and morphologies of the residual carbons of poly(PH-ddm) and poly(PH/PHB) after combustion were studied by SEM. It was found that the pores in carbon layer of poly(PH/PHB) were dense and homogeneous. Furthermore, the pyrolytic volatile products of poly(PH-ddm) and poly(PH/PHB) were analyzed by TGA-IR and Py-GC/MS to discuss the degradation and flame retardant mechanism.

Dehydrogenative Synthesis of Quinolines, 2-Aminoquinolines, and Quinazolines Using Singlet Diradical Ni(II)-Catalysts.

Simple, straightforward, and atom economic methods for the synthesis of quinolines, 2-aminoquinolines, and quinazolines via biomimetic dehydrogenative condensation/coupling reactions, catalyzed by well-defined inexpensive and easy to prepare singlet diradical Ni(II)-catalysts featuring two antiferromagnetically coupled singlet diradical diamine type ligands are described. Various polysubstituted quinolines, 2-aminoquinolines, and quinazolines were synthesized in moderate to good yields from different low-cost and readily accessible starting materials. Several control experiments were carried out to get insight into the reaction mechanism which shows that the nickel and the coordinated diamine ligands participate in a synergistic way during the dehydrogenation of alcohols.

Supramolecular Networks from Block Copolymers Based on Styrene and Isoprene Using Hydrogen Bonding Motifs—Part 2: Dynamic Mechanical Analysis

Thermo-reversible supramolecular networks from polyisoprene-block-polystyrene-block-polyisoprene (ISI) triblock copolymers with short, functionalized polyisoprene (PI) blocks were investigated. Functional groups along the PI blocks were hydroxyl groups, ester groups with a carboxylic end-group (-O-CO-CH2-CH2-COOH), and urethane groups with an amine end-group—synthesized from various types of diamines—(-O-CO-NH-R-NH2). Dynamic mechanical analysis (DMA) was performed at temperatures above Tg of polystyrene (PS) to investigate the influence of the different functional groups, the molecular weight, and the composition of the triblock copolymers on the materials’ properties. Furthermore, comparisons to DMA results of diblock copolymers, modified in the same way, will be presented. Arising reversible and irreversible processes observed during DMA experiments will be compared to results from temperature-dependent Fourier transform infrared (FTIR) spectroscopy. For the elaborated systems, the transition from reversible, hydrogen-bonded to permanently cross-linked networks was observed at around 150 °C.

Supramolecular Networks from Block Copolymers Based on Styrene and Isoprene Using Hydrogen Bonding Motifs-Part 1: Synthesis and Characterization.

The combination of controlled anionic polymerization and subsequent introduction of hydrogen bonding groups was established to form thermo-reversible, supramolecular networks. Several polyisoprene-block-polystyrene-block-polyisoprene (ISI) copolymers—with polystyrene (PS) as the main block, and consequently giving the decisive material characteristics—were synthesized. The novel modification approach to post-functionalize the polyisoprene (PI) end-blocks and to introduce different motifs, which are able to form self-complementary hydrogen bonds, was attained. In the first step, hydroxylation was accomplished using 9-borabicyclo[3.3.1]nonane. Starting from the hydroxylated polymer, esterification with succinic anhydride was implemented to form an ester group with carboxylic end-group (-O-CO-CH2-CH2-COOH). In a second approach, 1,1’-carbonyldiimidazole was used as coupling agent to introduce various types of diamines (diethylenetriamine, triethylentetramine, and 2,6-diaminopyridine) to prepare urethane groups with amine end-group (-O-CO-NH-R-NH2). 1H NMR spectroscopy was used to confirm the successful synthesis and to calculate the degree of functionalization Df. Differential scanning calorimetry (DSC) showed a difference of the glass transition temperature Tg between unfunctionalized and functionalized block copolymers, but no greater influence between the different types of modification, and thus, on the Tg of the PS block. In temperature dependent FTIR spectroscopy, reversible processes were observed.

Reactivity of orthophthalaldehyde with aliphatic, alicyclic and aromatic primary diamines: Electrochemical study and mechanistic considerations

The reactions of OPA with eight primary diamines were electrochemically monitored and the main products were isolated and identified. Various types of diamines were used: two non-vicinal α,ω-diaminoalkanes, four vicinal 1,2-diamino(cyclo)alkanes and two aromatic diamines. The results showed three electrochemical patterns: α,ω aliphatic diamines and both aromatic diamines exhibited only consumption of the parent OPA without observation of any electroactive intermediate or product; aliphatic and alicyclic vicinal diamines react with OPA under fast formation of reducible intermediate and its slow follow-up reaction yielding reducible product. A special case represents 1,2-trans-diaminocyclohexane exhibiting different products with regard to its cis-isomer. The main reaction products in all cases are derivatives of indano[1,2-a]benzimidazole and not bis-Schiff bases discussed in the literature.It has been found that the reaction of non-vicinal diamines with OPA is much faster than that of the vicinal diamines. The UV–vis monitoring revealed that the reaction of OPA with vicinal, as well as non-vicinal diamines results in the same type of product, hence the mentioned difference in the electrochemical pattern is caused by different kinetics. The slower reaction rate can be caused by lower nucleophilicity of vicinal diamines, where stronger electronic communication of vicinal amino groups takes place. This effect manifests itself as larger difference between the first and second pKa of the two amine groups and the comparison of HOMOs supported this interpretation.

Emergence of temperature-dependent and reversible color-changing properties by the stabilization of layered polydiacetylene through intercalation

The stimuli-responsive color-changing properties of functional polymers are applied to the development of sensing and imaging devices. Tuning the stimuli responsivity is required for a wide range of applications. Polydiacetylene (PDA) derivatives show color changes with the application of external stimuli, such as heat and mechanical stress. Our group has focused on the layered crystal structure of PDA and its intercalation chemistry. The original layered PDA shows an irreversible color transition from blue to red upon heating to the threshold temperature. Here, we found that alkyldiamine-intercalated PDA possessed different color-changing properties, such as a higher color transition temperature and a temperature-dependent and reversible color change, than the original PDA. As the alkyl-chain length increased, the color-changing behavior gradually converted from the irreversible color transition type to the reversible temperature-dependent one. Since the intercalated diamine had a stabilizing effect on the layered structure, the stimuli responsivity varied according to the type of diamine. The results suggest that the stimuli-responsive color-changing properties of layered PDA can be finely and systematically tuned by the intercalation of organic guests. Polydiacetylene (PDA) derivatives exhibit color change with application of external stimuli, such as heating and mechanical stress. The original layered PDA shows the irreversible color transition from blue to red with heating at the threshold temperature. Here we found that the alkyldiamine-intercalated PDA induced the different color-change properties, such as the raise of the color-transition temperature, the temperature-dependent color-change, and the reversible color change. The intercalated diamines have the stabilization effect of the layered polymer. The stimuli-responsive color-change properties can be tuned by the intercalated organic guests.