Low Molecular Weight Polyamide Research Articles

Study on the synthetic mechanism of monodispersed polystyrene-nickel composite microspheres and its application in facile synthesis of epoxy resin-based anisotropic conductive adhesives

Monodispersed polystyrene-nickel (PS-Ni) composite microspheres were used to enhance the conductivity of epoxy-based anisotropic conductive adhesive (ACA) for the first time. Specifically designed PS-Ni composite microspheres were used as conductive elements to construct anisotropic conductive arrays. The surface microstructure and morphology of the prepared PS-Ni composite microspheres were tuned by controlling the implementation method of electroless plating and concentration of Ni precursor. The structural composition, thermal properties, and electrical properties of PS-Ni composite microspheres were analyzed. In addition, diglycidyl ether of bisphenol-A (DGEBA) epoxy resin and low molecular weight polyamide resin were used as the matrix resin and curing agent, respectively. The optimal process parameters were employed and predicted based on the curing kinetics. A simple strategy was developed for the preparation of anisotropic conductive binders (viz. PS-Ni/EP-ACAs) via physical doping by addition of terminal carboxyl-terminated butadiene acrylonitrile (CTBN) copolymer and additives. PS-Ni/EP-ACAs exhibited satisfactory anisotropic electrical properties in fabricated components due to submicron structures composed of PS-Ni composite microspheres with excellent integrated properties in the anisotropic conducting array. Therefore, the theoretical concept and fabrication mean proposed in this study showed great potential and practical application in large-scale ACAs preparation.

Study on the compounding of a new type of trimer epoxy resin curing agent

AbstractIn this paper, bisphenol A (BPA), epichlorohydrin (ECH), and isocyanate trimer (TDI‐T) are used as raw materials to synthesize a high toughness/trimer epoxy resin by graft copolymerization. It was cured at room temperature with low molecular weight polyamide 650 (PA650)/isophorone diamine (IPDA) and low molecular weight polyamide 650/triethylene tetramine (TETA) composite curing system respectively. The cured products of the two compound systems were studied by Fourier transform infrared spectroscopy (FT‐IR), differential scanning calorimetry (DSC), thermogravimetry (TG), and mechanical property testing. The results show that with the increase of TETA and IPDA curing agents, the heat released during the curing process of the two systems also greatly increases, and the temperature rises from the initial 33.9–69.7°C and 52.8°C. The curing time is shortened from a few days to a few hours, and the controllability of the curing time is effectively realized. When the ratio of triethylene tetramine to low molecular weight polyamide 650 is 2.86:100, the compressive strength is the best, reaching 112.7 MPa, 12% higher than pure polyamide as curing agent, and the specimen can be completely restored to its original shape in a few minutes. When the ratio of TETA to PA650 is 2.86:100, the elongation at break reaches 21.4%.

Isothermal Kinetics of Epoxyphosphazene Cure

The influence of epoxycyclophosphazene modifier on the process of epoxy-amine curing was studied by differential scanning calorimetry (DSC). The study revealed that the curing process of epoxyphosphazene binders with 4′4′diaminodiphenylsulfone (DDS) provides more complete curing of the formulations in comparison with ones applying low molecular-weight polyamide curing agent (L-20). The isothermal kinetics of curing was described by means of model fitting and the isoconversional approach (Friedman method). Accurate n-order approximation was obtained for all systems under study. In particular, the 2-order equation fits well with the main part of curing excluding high degrees of conversion. The process of curing could be distinguished into three zones. The transition from zone 2 to zone 3 correlates with gelation. According to the isoconversional analysis by Friedman method, the diffusion-controlled mechanism is found at final stage of curing.

Thiokol oligomer functionalized MWCNTs for epoxy nanocomposites

PurposeThis paper aims to feature preparation and characterization of thiokol oligomer functionalized MWCNTs/epoxy nanocomposites using low molecular weight polyamide as curing agent.Design/methodology/approachFirst, thiokol oligomer functionalized MWCNTs (MWCNTs-TO) were prepared through hydroxylation, silanization and graft modification of MWCNTs. The nanocomposite specimens were fabricated through sonication and cast moulding process. The authors then investigated the impact of MWCNTs-TO content on mechanical and thermal properties of the nanocomposites.FindingsMWCNTs-TO with grafting ratio of 17.5 Wt.% was synthesized and characterized with X-ray photoelectron spectroscopy, thermal gravimetric analysis, Fourier transform infrared and scanning electron microscopy. The obtained epoxy nanocomposites exhibit improved mechanical properties and thermal stability with MWCNTs-TO added. Moreover, desirable results were obtained at 0.75 Wt.% of MWCNTs-TO loading: the young’s modulus, tensile, flexural and impact strength increased by 24.6,72.8,34.8 and 82.7%, respectively, compared to the neat epoxy. The improvement of mechanical properties is mainly attributed to enhanced interfacial interaction and dispersion between the covalent functionalized MWCNTs and epoxy matrix.Research limitations/implicationsA flexible thiokol oligomer was successfully grafted onto MWCNTs via a mild route. Nanocomposites with excellent interfacial interaction and dispersion between MWCNTs-TO and the epoxy matrix have been successfully fabricated and investigated.Practical implicationsThis method provided a mild and practical approach to improve the performance of MWCNTs epoxy nanocomposites.Originality/valueA flexible thiokol oligomer was successfully covalent grafted onto MWCNTs via a mild route. Nanocomposites with excellent interfacial interaction and dispersion between MWCNTs-TO and the epoxy matrix have been successfully fabricated and investigated.

Nghiên cứu chế tạo lớp phủ bảo vệ bo mạch điện tử trên cơ sở nhựa Epoxy biến tính bằng cao su Polysulfide lỏng

This paper presents some results in studying and producing a coating to protect printed circuit board from tropical environmental impact. We have tested the protective ability of the coating based on epoxy resin ED-20 and low-molecular weight polyamide resin L-20 modified by liquid polysulfide rubber NVB-2. The testing data has shown that the coating has high mechanical, environmental and electrical durability.

Structure and properties of a low viscosity acrylate based flexible epoxy resin

ABSTRACTA series of low viscosity acrylate‐based epoxy resin (AE)/glycol diglycidyl ether (GDE) systems were prepared. The effect of GDE and low molecular weight polyamide (LPA) content on the rheological behavior, phase structure, damping, and mechanical properties were studied by differential scanning calorimeter (DSC), viscometer, scanning electron microscopy (SEM), dynamic mechanical thermal analysis (DMTA), and electro mechanical machine. The viscosity of the uncured AE systems decreased significantly after the incorporation of GDE. The damping properties were found to decrease slightly with the increasing GDE and LPA content. The tensile strength of the cured AE/GDE samples enhanced significantly after the incorporation of GDE with at least 150% improvement for all the samples while it decreased slightly with increasing LPA content. The AE/GDE cured systems were intended for future use as structural damping materials. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 42959.

Solvent‐based and solvent‐free characterization of low solubility and low molecular weight polyamides by mass spectrometry: a complementary approach

Polyamides (PA) belong to the most used classes of polymers because of their attractive chemical and mechanical properties. In order to monitor original PA design, it is essential to develop analytical methods for the characterization of these compounds that are mostly insoluble in usual solvents. A low molecular weight polyamide (PA11), synthesized with a chain limiter, has been used as a model compound and characterized by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). In the solvent-based approach, specific solvents for PA, i.e. trifluoroacetic acid (TFA) and hexafluoroisopropanol (HFIP), were tested. Solvent-based sample preparation methods, dried-droplet and thin layer, were optimized through the choice of matrix and salt. Solvent-based (thin layer) and solvent-free methods were then compared for this low solubility polymer. Ultra-high-performance liquid chromatography/electrospray ionization (UHPLC/ESI)-TOF-MS analyses were then used to confirm elemental compositions through accurate mass measurement. Sodium iodide (NaI) and 2,5-dihydroxybenzoic acid (2,5-DHB) are, respectively, the best cationizing agent and matrix. The dried-droplet sample preparation method led to inhomogeneous deposits, but the thin-layer method could overcome this problem. Moreover, the solvent-free approach was the easiest and safest sample preparation method giving equivalent results to solvent-based methods. Linear as well as cyclic oligomers were observed. Although the PA molecular weights obtained by MALDI-TOF-MS were lower than those obtained by (1)H NMR and acido-basic titration, this technique allowed us to determine the presence of cyclic and linear species, not differentiated by the other techniques. TFA was shown to induce modification of linear oligomers that permitted cyclic and linear oligomers to be clearly highlighted in spectra. Optimal sample preparation conditions were determined for the MALDI-TOF-MS analysis of PA11, a model of polyamide analogues. The advantages of the solvent-free and solvent-based approaches were shown. Molecular weight determination using MALDI was discussed.

Morphologies and Properties of Epoxy Resin–Low Molecular Weight Polyamide Curing System Modified with Expanded Graphite

Abstract. Expanded graphite (EG) was prepared through high-temperature oxidation using natural flake graphite (NG). The curing system of epoxy resin (EP)-low molecular weight polyamide (LPA) was modified with expanded graphite. The mechanical property, thermal stability and electrical property, micro-structure and micro-morphology characterization of the curing system EP-LPA/EG were studied. The results showed that impact strength and thermal stability of the EP-LPA/EG increased with the addition of expandable graphite. Expandable graphite lowers the electrical resistivity of the complex curing system. SEM analysis indicates that expanded graphite dispersed homogeneously in the EP-LPA/EG curing system. The existence of EG made the curing system taking on loosen multiporous structure, and increased the interface effect of the EP-LPA/EG systems.

Novel, Fully Biobased Semicrystalline Polyamides

Novel, semicrystalline polyamides and co(polyamides) were synthesized from biobased sebacic acid (SA), 2,5-diamino-2,5-dideoxy-1,4;3,6-dianhydroiditol (diaminoisoidide, DAII) as well as from 1,4-diaminobutane (DAB), also known as putrescine in nature. Low molecular weight polyamides were obtained by melt polycondensation of the salts based on these monomers or by interfacial polycondensation. In order to increase their molecular weights the polyamide prepolymers were submitted to a solid state polymerization (SSP) process. The chemical structure of the polymers was confirmed by 2D NMR correlation spectra (COSY), heteronuclear multiple-bond correlation spectra (HMBC) and by FT-IR spectroscopy. In the present work, FT-IR and X-ray techniques were used as a tool for the investigation of the crystal structure of the polymers after SSP. The X-ray diffractograms of the polyamides point to crystals containing both 4.10- and DAII.10-based repeat units. Because of the presence of diaminoisoidide residues the synthesized fully renewable products exhibit tunable polarities and melting points. Since most commercial polyamides have a much higher melting point than their end application requires, especially for fiber applications, this simple adaption can result in a significant reduction of energy consumption during processing.

Hx, a Novel Fluorescent, Minor Groove and Sequence Specific Recognition Element: Design, Synthesis, and DNA Binding Properties of p-Anisylbenzimidazole-imidazole/pyrrole-Containing Polyamides

With the aim of incorporating a recognition element that acts as a fluorescent probe upon binding to DNA, three novel pyrrole (P) and imidazole (I)-containing polyamides were synthesized. The compounds contain a p-anisylbenzimidazolecarboxamido (Hx) moiety attached to a PP, IP, or PI unit, giving compounds HxPP (2), HxIP (3), and HxPI (4), respectively. These fluorescent hybrids were tested against their complementary nonfluorescent, non-formamido tetraamide counterparts, namely, PPPP (5), PPIP (6), and PPPI (7) (cognate sequences 5'-AAATTT-3', 5'-ATCGAT-3', and 5'-ACATGT-3', respectively). The binding affinities for both series of polyamides for their cognate and noncognate sequences were ascertained by surface plasmon resonance (SPR) studies, which revealed that the Hx-containing polyamides gave binding constants in the 10(6) M(-1) range while little binding was observed for the noncognates. The binding data were further compared to the corresponding and previously reported formamido-triamides f-PPP (8), f-PIP (9), and f-PPI (10). DNase I footprinting studies provided additional evidence that the Hx moiety behaved similarly to two consecutive pyrroles (PP found in 5-7), which also behaved like a formamido-pyrrole (f-P) unit found in distamycin and many formamido-triamides, including 8-10. The biophysical characterization of polyamides 2-7 on their binding to the abovementioned DNA sequences was determined using thermal melts (ΔT(M)), circular dichroism (CD), and isothermal titration calorimetry (ITC) studies. Density functional calculations (B3LYP) provided a theoretical framework that explains the similarity between PP and Hx on the basis of molecular electrostatic surfaces and dipole moments. Furthermore, emission studies on polyamides 2 and 3 showed that upon excitation at 322 nm binding to their respective cognate sequences resulted in an increase in fluorescence at 370 nm. These low molecular weight polyamides show promise for use as probes for monitoring DNA recognition processes in cells.

Abstract 3521: Pharmacological modulation of Topoisomerase IIα expression and confluence-induced resistance to etoposide by a novel fluorescent HxIP polyamide

Abstract Pyrrole (P)-Imidazole (I) containing polyamides are small synthetic molecules which can target predetermined DNA sequences with high affinity and modulate gene expression by interfering with the binding of transcription factors to DNA. As a model system we have previously used the inverted CCAAT box 2 (ICB2) of the topoisomerase IIα promoter and shown that targeted polyamides inhibit the binding of the transcription factor NF-Y and induce expression of topo IIα in confluent cancer cells. Critical to this approach is the need for low molecular weight polyamides that readily enter in the nucleus. In this study, the fluorophore p-anisylbenzimidazolecarboxamido (Hx) moiety was rationally designed to mimic the recognition of A/T base pairs by two consecutive pyrrole units. The hybrid polyamide HxIP is the first example of a small fluorescent molecule that fluoresces significantly more intensely upon binding to its target sequence, 5′-TACGAT-3′ of the 5′-flank of ICB2. Sequence specificity was confirmed by DNAse I footprinting, with HxIP binding with increased affinity compared to the corresponding triamides/tetraamides (f-PIP/PPIP). Thermal denaturation, circular dichroism, and Surface Plasmon Resonance studies confirmed the sequence specificity of HxIP. A dose-dependent inhibition of protein binding to ICB2 by HxIP with complete abolition at concentrations >3 μM was seen in an Electrophoretic Mobility Shift Assay (EMSA). A supershift assay confirmed NF-Y binding to the target sequence. HxIP was also able to displace bound protein factors from DNA at the same concentrations. The incorporation of Hx in the hybrid molecule provides an intrinsic probe to directly monitor cellular uptake and migration into the nucleus. Confocal microscopy in both fixed and live NIH3T3 and A549 cells showed that HxIP is readily taken up by cells and quickly localises in the cell nucleus within 5 minutes. Exposure of confluent cells to 20-40 μM HxIP resulted in time-dependent upregulation of topo IIα expression, reaching levels comparable to those of proliferating cells within 24h as shown by immunoblotting analysis. Confluence-associated repression of topo IIα expression contributes to cellular resistance to agents such as etoposide. De-repression of topo IIα by pre-incubation with HxIP was shown to resensitise NIH3T3 cells to the cytotoxic effect of etoposide (MTT assay) and enhance its DNA damaging effects by increasing levels of etoposide-induced DNA strand breaks as assessed by the single cell gel electrophoresis (comet) assay and the phosphorylation of H2AX. Subcellular localisation of HxIP and potential synergies with etoposide treatment is currently being investigated in vivo against human tumour xenografts. Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3521.

Investigation on thermo-stabilization effect and nonisothermal degradation kinetics of the new compound additives on polyoxymethylene

An increase in the thermal stability of several new additives on polyoxymethylene (POM) was attempted via thermogravimetric analysis (TGA) (static state) and balance torque testing (dynamic state), which truly reflected the processing in practice. The thermal stability of POM was improved by adding some of additives actually, especially for the compound stabilizer with oxidized polyethylene wax (OPE), low molecular weight polyamide 6 (LMWPA6) and triphenyl phosphate (TPP) from the static and dynamic data. Furthermore, the kinetic parameters for compound stabilizers of POM degradation were calculated from thermogravimetry (TG) curves by Coats-Redfernd method. The results reveal that the degradation temperatures of POM can be obviously raised by compound stabilizers OPE/LMWPA6/TPP. The long-term thermo-stability test of POM shows that POM with stabilizing system above has no obvious decrease in impact strength after storage duration of 15 days in an oven at 140 °C.

Formation of porous epoxy monolith via concentrated emulsion polymerization

Step polymerization was introduced into the concentrated emulsion templating method and was illustrated with the preparation of porous epoxy monolith. A solution of diglycidyl ether of bisphenol-A (DGEBA), its curing agent low molecular weight polyamide resin, and surfactant nonyl phenol polyoxyethylene ether in 4-methyl-2-pentanon as a solvent was used as the continuous phase, an aqueous suspension of colloidal silica as the dispersed phase of the concentrated emulsion. After the continuous phase polymerized and the dispersed phase removed, a porous material is obtained. The key point in this work is to find a compromise between the rates of curing and phase separating and thus achieve a kinetic stability of the concentrated emulsion. The effects of loading of colloidal silica, the pre-curing of the epoxy precursors, and the volume fraction of the dispersed phase were systematically investigated.

A flame-retardant epoxy resin based on a reactive phosphorus-containing monomer of DODPP and its thermal and flame-retardant properties

A flame-retardant epoxy resin (EP) was synthesized based on a novel reactive phosphorus-containing monomer, 4-[(5,5-dimethyl-2-oxide-1,3,2-dioxaphosphorinan-4-yl)oxy]-phenol (DODPP), and its structures were characterized by FTIR, 1H NMR and 31P NMR spectra. The DODPP–EP 3/LWPA (low molecular weight polyamide), which contains 2.5% phosphorus, can reach UL-94 V-0 rating and a limiting oxygen index (LOI) value of 30.2%. The thermal properties and burning behaviours of cured epoxy resins were investigated by differential scanning calorimeter (DSC), thermogravimetry (TG), LOI, UL-94 tests and cone calorimetry. The morphologies of residues of cured epoxy resins were investigated by scanning electron microscopy (SEM). DSC shows that the glass-transition temperatures of cured epoxy resins decrease with increasing phosphorus content. TGA shows that the onset decomposition temperatures and the maximum-rate decomposition temperatures decrease, while char yields increase, with the increase of phosphorus content. The data from the cone calorimeter tests give the evidence that heat release rate (HRR), peak heat release rate (PHRR), average heat release rate (Av-HRR), average mass loss rate (Av-MLR) and the fire growth rate index (FIGRA) decrease significantly for DODPP–EP 3/LWPA. SEM shows that the DODPP–EP 3/LWPA forms lacunaris and compact charred layers which inhibit the transmission of heat during combustion.

Polyamide‐enhanced flame retardancy of ammonium polyphosphate on epoxy resin

AbstractAn attractive intumescent flame retardant epoxy system was prepared from epoxy resin (diglycidyl ether of bisphenol A), low molecular weight polyamide (cure agent, LWPA), and ammonium polyphosphate (APP). The cured epoxy resin was served as carbonization agent as well as blowing agent itself in the intumescent flame retardant formulation. Flammability and thermal stability of the cured epoxy resins with different contents of APP and LWPA were investigated by limited oxygen index (LOI), UL‐94 test, and thermogravimetric analysis (TGA). The results of LOI and UL‐94 indicate that APP can improve the flame retardancy of LWPA‐cured epoxy resins. Only 5 wt % of APP can increase the LOI value of epoxy resins from 19.6 to 27.1, and improve the UL‐94 ratings, reaching V‐0 rating from no rating when the mass ratio of epoxy resin to LWPA is 100/40. It is much interesting that LOI values of flame retardant cured epoxy resins (FR‐CEP) increase with decreasing LWPA. The results of TGA, FTIR, and X‐ray photoelectron spectroscopy (XPS) indicate that the process of thermal degradation of FR‐CEP consists of two main stages: the first stage is that a phosphorus rich char is formed on the surface of the material under 500°C, and then a compact char yields over 500°C; the second stage is that the char residue layer can give more effective protection for the materials than the char formed at the first stage do. The flame retardant mechanism also has been discussed according to the results of TGA, FTIR, and XPS for FR‐CEP. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Nylon 6 nanocomposites: the effect of matrix molecular weight

Organoclay nanocomposites based on three different molecular weight grades of nylon 6 were prepared by melt processing using a twin screw extruder. Mechanical properties, transmission electron microscopy, wide-angle X-ray diffraction, and rheological measurements were used to characterize the three types of composites. Tensile modulus and yield strength were found to increase with increasing concentration of clay, while elongation at break decreased. Izod impact strength was relatively independent of clay content for the higher molecular weight composites, but slightly decreased with increasing clay content for the lowest molecular weight polyamide. In general, nanocomposites based on the higher molecular weight polyamides yielded superior composite properties, having higher degrees of clay exfoliation, higher stiffness and yield strength values, and marginal loss of ductility as compared to nanocomposites based on the low molecular weight polyamide. Differences in properties between the three types of composites were attributed to differences in melt rheology. Capillary and dynamic parallel plate data revealed sizeable differences in the levels of shear stress between each nanocomposites system. A mechanism for exfoliation during melt mixing is outlined.

The (Co)Polymerization of the Cyclic Diamide 1,6-Diazacyclododecane-7,12-Dione

Abstract It is demonstrated for the first time that the cyclic diamide 1,6- diazacyclododecane-7,12-dione (c-4) can be polymerized. Polyamide 46 was prepared by thermal or hydrolytic ring-opening polymerization of c-4. c-4 polymerized in the melt to form polyamide 46, containing approximately one-third of the original c-4. Due to possible degradation of c-4 near its melting point, the polyamide 46 formed possibly contained a crosslinked fraction which was insoluble. Therefore, the thermal behavior deviated from that of Stanyl (a commercial polyamide 46 from DSM, The Netherlands). Furthermore, polyamide 46 was prepared by anionic polymerization of c-4 in N-methyl-2-pyrrolidone solution at 202°C. c-4 polymerized with NaH and 1,6-hexamethylene diisocyanate as catalysts. Almost all c-4 was converted to polyamide 46. Due to possible crosslinking, the polyamides had difficulties in dissolving. Furthermore, the thermal behavior of this low molecular-weight polyamide 46 deviated from that of Stanyl, but solid-state postcondensation had a positive effect on the melting point. Then copolyamides of e-caprolactam (CL) and c-4 were prepared by anionic ring-opening copolymerizations. The cyclic monomers polymerized in the melt with lactam magnesium bromide and isophthaloyl-bis-caprolactam as catalysts. It was demonstrated that approximately all c-4 was copolymerized with CL at 180°C. At 200°C only ∼ 30% was incorporated. The copolymerization of a maximum of 8.5 mol% c-4 in polyamide 6 showed no effect on the thermal behavior and crystallinity as compared to polyamide 6.

Thermally reactive aromatic polyamides

Abstract2,5‐Bis(phenylethynyl)terephthaloyl chloride and 4,6‐bis‐(phenylethynyl)isophthaloyl chloride were synthesized in a multistep reaction scheme from 2,5‐dibromoterephthaldehyde and 4,6‐dibromoisophthaldehyde, respectively. Low temperature solution polycondensation of these novel monomers and tolane‐2,4′‐dicarbonyl chloride with aromatic diamines yielded aromatic polyamides containing phenylethynyl moieties. Inherent viscosities of 0.20–0.51 dL/g were recorded. Attempts to carry out the homopolymerization of 2‐(3‐aminophenylethynyl)benzoyl chloride hydrochloride under similar conditions led to low molecular weight polyamide. Under differential scanning calorimetry and thermal mechanical analysis, the polyamides exhibited strong exotherms with onset occurring in the 185–225°C range. The exotherms were attributable to intramolecular cycloaddition of phenylethynyl moieties with amide groups to give polybenzalphthalimidine structures. Curing of a pressed pellet specimen for 16 h at 250°C under a nitrogen atmosphere resulted in partial conversion to a polybenzalphthalimidine structure with a concomitant increase in the polymer glass transition temperature. Isothermal aging in air of the cured specimen at 316°C (600°F) led to 25% weight loss after 200 h.

Preparation and photolysis of polyamides having coumarin dimer component

AbstractThe ring‐opening polyaddition reaction of anti and syn head‐to‐head Coumarin dimers with diamines and the photocleavage behavior of the resulting polyamides were investigated. Anti head‐to‐head Coumarin dimer successfully reacted with aliphatic and aromatic diamines in an aprotic polar solvent to give corresponding high molecular weight polyamides. The polyamides showed good film forming ability and exhibited solubility behavior typical of polyelectrolytes. Furthermore, these polyamides were found to undergo exclusively asymmetric photocleavage on the cyclobutane rings in the polymer main chain to give a fumaramide unit with elimination of 2,2′‐dihydroxystilbene. On the other hand, syn head‐to‐head Coumarin dimer gave only low molecular weight polyamides. These polymerization and photocleavage behaviors were elucidated in comparison with those of model reactions.

Elimination and addition reactions. Part XXVII. Addition of amides to electrophilic alkenes

Treatment of amides from primary amines with strong bases and electrophilic alkenes (acrylonitrile or p-tolyl vinyl sulphone) gives products derived from N-alkylation of the amide. When amides without an N–H bond are used, no reaction occurs unless the amide gives a stabilised carbanion on proton abstraction; C-alkylation then occurs. When N- and C-alkylation can compete, N-alkylation is preferred.Dialkylation of diamides occurs readily, and evidence for alkylation of a low molecular weight polyamide has been obtained. Alkylation of Nylon 6 and Nylon 66, however, does not occur to an appreciable extent under the conditions used for the other amides.