Polyamide Segments Research Articles

Six-membered ring-reinforced flexible high-elongation block polyamide as strong and multi-reusable hot melt adhesive

This study presented the synthesis and characterization of polyester block polyamide hot melt adhesives (PPHMAs) with high adhesion strength and toughness. The PPHMAs demonstrated an adhesion strength of 11.04 MPa and toughness of 22.54 MJ·m−3, making them suitable for various substrates such as aluminum, copper, and stainless steel. The polyamide segments synthesized from dimer acid and 2-methyl-1,5-diaminopentane exhibited characteristics of softness and high elongation. Using isophorone diamine as a reinforcing agent introduced a stable six-membered ring structure, which enhanced the polymer's rigidity and strength, thus meeting the requirements for polyamide segments to function as the hard segments in block polymers. A trace amount of Tris (2-aminoethyl) amine provided the cross-linking sites which are similar to those in neuronal structures. The polyester segments, which were synthesized from poly (propylene glycol) diglycidyl ether and sebacic acid, served as the soft segments in the block polymer and were connected to the hard segment via amide bonds. The addition of the polyester segments enhanced the non-covalent molecular interactions within PPHMAs, leading to dynamic crosslinking properties. The adhesive maintained stable adhesion even after six cycles, which showcased its durability. Furthermore, the PPHMAs exhibited notable chemical resistance. It retained over 60 % adhesion strength after exposure to some chemical solvents including artificial seawater, 5 % NaOH solution, 5 % HCl solution, and DMSO for 24 h. These findings offered a novel approach to enhancing the adhesion strength and toughness of conventional thermoplastic hot melt adhesives.

A Disulfide‐Based Poly(ether‐b‐amide) Copolymer with Rapid Self‐healing Ability under Moderate Conditions†

Comprehensive SummaryA disulfide‐based poly(ether‐b‐amide) copolymer with rapid self‐healing capability under moderate conditions was synthesized from 4,4’‐dithiodibutyric acid (DTDBA), isophorondiamine (IPDA) and poly(tetramethylene oxide) (PTMO) based on a two‐step method. The incorporation of IPDA with asymmetric structure and substantial steric hindrance not only effectively decreased the number of regular H‐bonds, but also inhibited the crystallization of polyamide segments, imparting the synthesized poly(ether‐b‐amide) copolymer with an amorphous structural feature. Based on the coordination of segmental diffusion and recombination of disulfide bonds and hydrogen bonds, the scratches and damaged mechanical properties of PEBADS‐I611 could be completely self‐healed after healing at 40 °C for only 11 min and 3 h, respectively.

Enhancing the Wettability of Fibre Surface: A Comparative Experimental Study of Different Surface Activation Principles on Single Polyamide Fibre

In this study, we have compared three different principles of surface activation with regard to their effects on the properties of single polyamide fibres. The techniques used include the complexation-mediated surface treatment using CaCl2/EtOH/H2O solution (CEW), the atmospheric pressure plasma treatment with air (APPA) and grafting polymerisation process with 2- hydroxyethyl methacrylate (HEMA). The CEW modification, the plasma treatment and the grafting process induced a decrease in advancing contact angle and thus led to an improved wettability of the polyamide fibre. While for the CEW treatment, the decrease was solely due to a change in topography such as increased surface roughness leading to increased capillary effect, for the APPA and grafting technique the decrease was attributed to a combination of increased surface roughness and increased amount of oxygen or nitrogen-containing groups as detected by XPS. In addition, the fibre fineness decreased in the case of CEW treatment due to a dissolution of polyamide segments during the modification, while it increased in the grafting process due to an additional grafted layer. However, an increase in wetted length was observed for most samples, which was attributed to the increased waviness of the fibres. All treatments induced a decrease in fibre tensile strength that decreased with increasing treatment intensity.

Adding Polypeptides to the Toolbox for Redox-Switchable Polymerization and Copolymerization Catalysis

Bis(imino)pyridine (BIP) iron alkoxide complexes act as catalysts to efficiently polymerize N-carboxyanhydrides (NCAs), including γ-benzyl-l-glutamate NCA (BLG-NCA) and sarcosine NCA (Sar-NCA), at room temperature. Reaction rates were greatly enhanced with the addition of mild Lewis acids, such as [CoCp2][BArF24], which work cooperatively with the iron-based catalysts to facilitate NCA polymerization. The reactivity of (2,6MeBIP)FeOCH2C(CH3)3 with Sar-NCA was combined with its known reactivity for ε-caprolactone polymerization to form diblock and triblock copoly(ester-b-peptides) through sequential addition of lactone and NCA monomers. Redox-switchable polymerization reactions were developed by iteratively exposing the catalyst to redox reagents and Sar-NCA or cyclohexene oxide. The orthogonal reactivity demonstrated by the catalyst in its oxidized and reduced states led to the synthesis of diblock and triblock copoly(ether-b-peptides). Polyether segments were synthesized with the catalyst in its oxidized state, while the polyamide segments were synthesized with the catalyst in its reduced state. Both copolymerization reactions developed here are rare examples where NCA polymerization reactions can be combined with other ring-opening polymerization reactions to make copolymers containing polypeptides and other functional monomers.

The crystallinity of chemically bonded PA‐PTFE‐oil compounds by X‐ray diffraction and DSC

AbstractOne of the major shortcomings of compounding polyamide (PA), polytetrafluoroethylene (PTFE), and olefinic oils is the fact that they are incompatible. To overcome this issue, using energy radiation in the presence of oxygen leads to the breakage of the PTFE chain to generate hydrophilic functional groups (COF, COOH) and peroxy radicals. The created functional groups and radicals can be used to induce a chemical bond between PA and PTFE as well as between PTFE and olefinic oil molecules. In addition, the hardness of compounds significantly influences the application of materials as solid‐lubricant. It is well known that crystallinity affects the hardness of materials. In the presented study, the effects of the chemical bonding PA‐PTFE/PA‐PTFE‐oil on the crystallization behavior of various types of PA in chemically bonded PA‐PTFE‐oil‐chemically bonded compounds, which were prepared by reactive two‐step extrusion, were investigated via DSC and X‐ray diffraction. The crystallite size of PA46 and PA66 in PA‐PTFE‐chemically bonded (cb) compounds was significantly increased compared with pure PA. At the same time, the d‐spacings of the PA segment in PA‐PTFE compounds were significantly narrower. Due to the chemical coupling, the compounds showed a slight change in hardness compared with pure PA.

Covalent organic frameworks-incorporated thin film composite membranes prepared by interfacial polymerization for efficient CO2 separation

Thin film composite (TFC) membranes with nanofillers additives for CO2 separation show promising applications in energy and environment-related fields. However, the poor compatibility between nanofillers and polymers in TFC membranes is the main problem. In this work, covalent organic frameworks (COFs, TpPa-1) with rich NH groups were incorporated into polyamide (PA) segment via in situ interfacial polymerization to prepare defect-free TFC membranes for CO2/N2 separation. The formed covalent bonds between TpPa-1 and PA strengthen the interaction between nanofillers and polymers, thereby enhancing compatibility. Besides, the incorporated COFs disturb the rigid structure of the PA layer, and provide fast CO2 transfer channels. The incorporated COFs also increase the content of effective carriers, which enhances the CO2 facilitated transport. Consequently, in CO2/N2 mixed gas separation test, the optimal TFC (TpPa0.025-PIP-TMC/mPSf) membrane exhibits high CO2 permeance of 854 GPU and high CO2/N2 selectivity of 148 at 0.15 MPa, CO2 permeance of 456 GPU (gas permeation unit) and CO2/N2 selectivity of 92 at 0.5 MPa. In addition, the TpPa0.025-PIP-TMC/mPSf membrane also achieves high permselectivty in CO2/CH4 mixed gas separation test. Finally, the optimal TFC membrane showes good stability in the simulated flue gas test, revealing the application potential for CO2 capture from flue gas.

Microphase separation/crosslinking competition-based ternary microstructure evolution of poly(ether-b-amide).

The temperature dependence of the rheological properties of poly(ether-b-amide) (PEBA) segmented copolymer under oscillatory shear flow has been investigated. The magnitude of the dynamic storage modulus is affected by the physical microphase separation and irreversible crosslinking network, with the latter spontaneously forming between the polyamide segments and becoming the dominant factor in determining the microstructural evolution at temperatures well above the melting point of PEBA. From the rheological results, the initial temperature of the rheological properties dominated by the microphase separation and crosslinking (Tcross) structures were determined, respectively. Based on the two obtained temperatures, the microstructure evolution upon the heating can be separated into the ternary microstructure domains: homogenous (temperature below ), microphase separation dominating (between and Tcross), and crosslinking dominating domains (above Tcross). When the PEBA is heated to above Tcross, the content of crosslinking network increases with time and temperature, leading to an irreversible and non-negligible influence on the rheological, crystallization, and mechanical properties. A more pronounced strain-hardening phenomenon during the uniaxial stretching is observed for the sample with a higher content of crosslinking network.

Enhanced CO2-selective behavior of Pebax-1657: A comparative study between the influence of graphene-based fillers

Mixed matrix membranes (MMMs) containing graphene-based fillers have attracted considerable attention in the field of gas separation. In this study, two types of graphene derivatives (Graphene (G) and Graphene Oxide (GO)) were embedded into the poly-ether-block-amide (Pebax) based MMM to investigate and compare CO2/N2 separation at various filler loadings (0.3–1 wt%). The morphologies of the prepared neat Pebax and MMMs were characterized by SEM, XRD, FTIR and DSC. Compared with the neat Pebax, the permeability of all gases was increased by adding filler content in the MMMs due to the crystallinity decrement of the polyamide (PA) segment. The best separation performance of the Pebax/G MMMs occurred at 0.7 wt%, where the CO2 permeability increased from 26.51 to 44.78 Barrer (~1.7 times). Also, for the Pebax/GO MMMs, the CO2 permeability was increased up to 58.96 Barrer (~2.2 times) by adding 0.5 wt% filler. This further gas permeation increment for the Pebax/GO sample was attributed to the higher affinity of GO nanosheets to CO2 sorption, which can facilitate CO2 gas transition through the membrane matrix. Moreover, the CO2/N2 ideal selectivity increased from 74.26 for the neat Pebax to 111.95 (~1.5 times) and 120.72 (~1.62 times) by adding 0.7 wt% G (Pebax/G-0.7) and 1 wt% GO (Pebax/GO-1) into Pebax, respectively. As a consequence, graphene derivatives can be recognized as a promising developer of permselectivity (permeability and selectivity) of the MMMs.

A novel inherently flame-retardant thermoplastic polyamide elastomer

Thermoplastic polyamide elastomers (TPAEs) are a new and important member of the thermoplastic polymer elastomers (TPEs) family, and the flame retardation of TPAEs is a big challenge due to the deterioration of their properties. In this work, we have successfully designed and synthesized the first “inherently” flame-retardant TPAE by introducing a phosphorus-containing group (DDP) into the macromolecular chains through P-C covalent bonds. The properties of TPAEs can be regulated by controlling the contents and distribution of polyamide (PA) segments as a hard segment, polyethylene glycol (PEG) as a soft segment, and DDP as a flame retardant unit during the synthetic process. The resulting TPAEs can achieve a V-0 rating in the UL-94 test and a limiting oxygen index of higher than 35.0%. The enhancement of flame retardancy is attributed to the droplet-promoting mechanism and the free radical quenching effect in the vapor phase. Unfortunately, the density of the inter-chain H-bonding and crystallinity of the PA segments regions decreased with the incorporation of DDP groups, which lead to the decrease of the tensile properties of TPAEs. However, the samples with high flame retardancy are still able to maintain 400% of elongation at break and 20 MPa of tensile strength, respectively, which have better comprehensive properties than typical commercial TPEs (Pebax®). Therefore, this novel inherently flame-retardant thermoplastic polyamide elastomer will exhibit a wider range of application potentials.

Polymerization of Meldrum's Acid and Diisocyanate: An Effective Approach for Preparation of Reactive Polyamides and Polyurethanes.

Meldrum’s acid (MA) is utilized as a monomer to polymerize with diisocyanates to result in polyamides, containing MA moieties at polymer chains. This reaction is also employed to prepare isocyanate-terminated polyamide segments which are utilized as a precursor for preparation of MA-containing polyurethanes. Based on the thermolysis reaction of MA groups, followed by ketene dimerization reaction, the reactive polyamides and polyurethanes show self-cross-linkable features. The cross-linked polyurethanes exhibit good film formability, thermal stability, and mechanical properties. A new MA-based polymerization method and a novel synthesis route for preparation of reactive polyamides and polyurethanes are demonstrated.

Structure-properties relationships of novel poly(carbonate-co-amide) segmented copolymers with polyamide-6 as hard segments and polycarbonate as soft segments

Novel poly(carbonate-co-amide) (PCA) block copolymers are prepared with polycarbonate diol (PCD) as soft segments, polyamide-6 (PA6) as hard segments and 4,4’-diphenylmethane diisocyanate (MDI) as coupling agent through reactive processing. The reactive processing strategy is eco-friendly and resolve the incompatibility between polyamide segments and PCD segments in preparation processing. The chemical structure, crystalline properties, thermal properties, mechanical properties and water resistance were extensively studied by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Differential scanning calorimetry (DSC), Thermal gravity analysis (TGA), Dynamic mechanical analysis (DMA), tensile testing, water contact angle and water absorption, respectively. The as-prepared PCAs exhibit obvious microphase separation between the crystalline hard PA6 phase and amorphous PCD soft segments. Meanwhile, PCAs showed outstanding mechanical with the maximum tensile strength of 46.3 MPa and elongation at break of 909%. The contact angle and water absorption results indicate that PCAs demonstrate outstanding water resistance even though possess the hydrophilic surfaces. The TGA measurements prove that the thermal stability of PCA can satisfy the requirement of multiple-processing without decomposition.

Improved Gas Separation of PEBAX-CSWCNTs Mixed Matrix Membranes

In the present study, mixed matrix membranes (MMMs) were prepared using PEBAX® 3000 as polymer matrix and single-wall carbon nanotubes (SWCNTs) functionalized with carboxyl groups as nanofillers. The effects of the nanofillers on separation of CO2/N2 and CO2/CH4 were investigated. The pristine PEBAX membrane indicated gas selectivity values of 23 and 13 for CO2/N2 and CO2/CH4, respectively. However selectivity of the modified membrane for gas pairs of CO2/N2 and CO2/CH4 improved to the values of 106.4 and 31.3, respectively. In other words, selectivity of modified membranes compared to those of unmodified ones enhanced greatly. The dramatic increase in gas selectivity of the mixed matrix membranes can be attributed to the polar groups of caboxyl-functionalized single-wall carbon nanotubes (CSWCNTs). While CO2 permeability of MMMs increaesd, permeability of nonpolar gases (N2 and CH4) decreased. FTIR spectra depicted that there were inter/intramolecular forces between ether and amide groups of the polymer chains. For PEBAX membrane filled with 10 wt% CSWCNTs, the peaks of C-O-C، N-H, and H-N-C=O functional groups shifted to lower values due to the formation of hydrogen bonds between polar carboxyl groups of CSWCNTs and amide/ether groups of PEBAX copolymer. Relative crystallinity values of the membranes with various CSWCNTs content were calculated using ΔHf data obtained from DSC measurements. Results demonstared that the rise in content of CSWCNTs brought about the decrement in crystallinity values of polyamide segments. The morphology of the membrane containing 10 wt% CSWCNTs was also investigated emplying AFM images, and a suitable compatability and adhere between PEBAX and CSWCNTs was last confirmed.

Strain-Induced Crystallization of Segmented Copolymers: Deviation from the Classic Deformation Mechanism

The classic deformation mechanism of the Gaussian model of Haward and Thackray was utilized to treat the true stress−strain behaviors of a family of novel polyether-b-amide segmented copolymers based on the crystalline hard segments of polyamide1012 and the amorphous soft segments of poly(tetramethylene oxide). The results showed that the deformation behaviors of the plastic copolymers abided by the Gaussian model, causing the modulus G of the strain-induced hardening process to depend on the weight percentage of the polyamide segments in the copolymers. By contrast, the deformation of elastomeric copolymers deviated from the model because of the occurrence of strain-induced crystallization in the soft polyether sections at large strains, which negated the Gaussian assumption; i.e., the random coil conformation was maintained even under substantial stretching. The onset point of deviation was, for the first time, quantitatively identified by in situ FTIR and further confirmed by in situ WAXD/SAXS.

SYNTHESIS, CHARACTERIZATION, AND GAS TRANSPORT PROPERTIES OF NEW COPOLY(ETHER-AMIDE)S CONTAINING BENZOPHENONE AROMATIC ISOPHTHALIC SEGMENT

Three new copoly(ether-amide)s based on polyether segments of different molecular weight (average molecular weight 400, 900 and 2000 g/mol) and polyamide segments obtained from 4,4’-diamine benzophenone (DBF) and isophthalic acid (ISO) are reported. The resulting new copoly(ether-amide)s have inherent viscosities ranging of 0.32 to 0.35 dL/g at concentration of 0.5 g/dL, and form dense membranes by solvent casting method. The gas transport properties of the new copoly(ether-amide) membranes for pure gases (He, CO2, O2, CH4, and N2) are studied at different pressures (2.0, 5.0, 7.5, and 10.0 atm) and at different temperatures (35-75 °C). The soft segment of polyether allows an increase in gas permeability coefficients, mainly CO2, in comparison with the values reported for DBFISO aromatic polyamide. However, an increase in polyether segment length decreases the overall permeability coefficients, because the polyether shows a strong tendency to crystallize.

Thermal properties and dielectric relaxation of a multi‐component poly(ether‐co‐amide) based on polyamide‐12

AbstractDSC, dielectric relaxation and dynamic mechanical thermal analysis (DMTA) were carried out on two multi‐component poly(ether‐co‐amide) samples having different weight ratios of polyamide prepared by condensation polymerization with 12‐aminododecanoic acid, adipic acid and polyetherdiamine consisting of poly(tetramethylene oxide) and poly(propylene oxide). The melting temperature was lowered by an increase in the weight ratio of the polyamide segment. Three relaxation modes, α′, αs and β, were found from dielectric relaxation measurements in different temperature ranges. The high temperature relaxation mode, α′, has a large dielectric constant, which disappears at the melting temperature of the polyamide crystal in the sample. The relaxation times for the segmental motion, αs, were different for the samples, which is attributed to the difference in the composition of the uncrystallized polyamide segments in the amorphous domain. The glass transition temperature estimated from DMTA is located between those of constituting polymers. On the other hand, the activation energy of β‐mode observed at low temperatures is the same for samples with different polyamide ratios, which is attributed to the local motion of the polyether segments. The uncrystallized polyamide segments are miscible with the polyether segments, which results in a lowering of the glass transition temperature of the amorphous domain and enlarges the temperature range of the rubber state of the copolymer due to the high melting temperature of the polyamide segments. © 2016 Society of Chemical Industry

Effects of different composition ratio on the dielectric relaxation and dynamic mechanical properties of poly(ω-dodecalactam-co -ε-caprolactam-co -propylene oxide) copolymers

The molecular dynamics of new poly (x-dodecalac- tam-co-e-caprolactam-co-propylene oxide) copolymers (DL/CL/ PAC) has been investigated by using dynamic mechanical ther- mal analysis (DMTA) and dielectric relaxation spectroscopy (DRS) measurements. The copolymers were synthesized via anionic poly- merization of relevant lactams activated with carbamoyl deriva- tives of telechelic hydroxyl terminated polypropylene oxide with isophorone diisocyanate (PAC). The calorimetric, X-ray diffrac- tion, and DMTA measurements were performed to recognize the influence of the composition ratio and the type of PAC on the physical, thermal, and mechanical properties of the synthesized copolymers. The DRS was used to study the frequency depend- ence of the dielectric permittivity of some isotherms from � 110 to 145 � C. Copolymerization of e-caprolactam with about 10 wt % x-dodecalactam results in a copolymer that has lower water absorption, a melting point close to that of polyamide 6 and has a high enough degree of crystallinity in respect to high storage modulus. Five dielectric relaxations have been observed in the dielectric spectra, three at lower temperature and two at higher temperature. The copolymers have two glass transition tempera- tures for polyamide segments and polyether blocks, indicating microphase separation in the copolymers. Other studies directed toward molecular dynamics of polyamide DL/CL/PAC copolymers have not been reported. V C 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 2518-2529, 2010

Study on the synthesis of poly(ether‐block‐amide) copolymer based on nylon6 and poly(ethylene oxide) with various block lengths

AbstractVarious segmented block copolyetheramides based on nylon6 (N6) and poly(ethylene oxide) (PEO) with different compositions and block length of the hard and soft segments were synthesized. The effect of composition of the hard and soft segments was studied via FTIR spectroscopy based on the characteristic peak of ester group at wave number of 1730 cm−1. The average block length of the hard and soft segments in block copolymers was determined from H‐NMR analysis. Differential thermal analysis thermograms confirmed a microphase separated morphology over a broad range of temperature, leading to two separated crystalline domains. An increase in the interconnectivity of the polyamide segments controlled by chain extension, greatly improved the formation of polyamide lamellae crystals determined by X‐ray diffractometry. Atomic force microscopy images indicated different morphologies of dispersed phase in the dominant phase, which plays an important role in their performance for membrane processes. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Synthesis of Well‐Defined Polybenzamide‐block‐Polystyrene by Combination of Chain‐Growth Condensation Polymerization and RAFT Polymerization

Well-defined diblock copolymers composed of poly(N-octylbenzamide) and polystyrene were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization of styrene with a polyamide chain transfer agent (CTA) prepared via chain-growth condensation polymerization. Synthesis of a dithioester-type macro-CTA possessing the polyamide segment as an activating group was unsatisfactory due to side reactions and incomplete introduction of the benzyl dithiocarbonyl unit. On the other hand, a dithiobenzoate-CTA containing poly(N-octylbenzamide) as a radical leaving group was easily synthesized, and the RAFT polymerization of styrene with this CTA afforded poly(N-octylbenzamide)-block-polystyrene with controlled molecular weight and narrow polydispersity.

Synthesis via Chain-Growth Condensation Polymerization and Gelating Properties of a Variety of Block Copolymers of Meta- and Para-Substituted Aromatic Polyamides

Well-defined diblock copolymers consisting of poly(m-benzamide)s with different N-alkyl groups and of poly(m-benzamide)s and poly(p-benzamide)s with different N-alkyl groups were synthesized by means of sequential chain-growth condensation polymerization. The polymerization of 3-(alkylamino)benzoic acid alkyl ester 1 was carried out with phenyl 4-methylbenzoate (3) as an initiator in the presence of 2.2 equiv of lithium 1,1,1,3,3,3-hexamethyldisilazide (LiHMDS) as a base, followed by addition of another kind of 1 or 4-(alkylamino)benzoic acid alkyl ester 2 to the reaction mixture to yield the block copolymer. The 4-octyloxybenzyl groups on the amide nitrogen in the obtained block copolymers were removed with trifluoroacetic acid (TFA) to give block copolymers containing an N−H polyamide segment. These block copolymers showed gelating properties at low concentration in various solvents ranging from aromatic to aprotic polar solvents. Scanning electron microscopic (SEM) images of the CH2Cl2 gel revealed tha...

Melting behavior of a poly(ether‐block‐amide) copolymer melt‐crystallized under quiescent, isothermal conditions

AbstractSegmented poly(ether‐block‐amide) copolymers are typically known as polyamide‐based thermoplastic elastomers consisting of hard, crystallizable polyamide block and flexible, amorphous polyether block. The melting characteristics of a poly(ether‐block‐amide) copolymer melt‐crystallized under various quiescent, isothermal conditions were calorimetrically investigated using differential scanning calorimetry (DSC). For such crystallized copolymer samples, their crystalline structures under ambient condition and the structural evolutions upon heating from ambient to complete melting were characterized using ambient and variable‐temperature wide‐angle X‐ray diffractometry (WAXD), respectively. It was observed that dependent of specific crystallization conditions, the copolymer samples exhibited one, two, or three melting endotherms. The ambient WAXD results indicated that all melt‐crystallized copolymer samples only exhibited γ‐form crystals associated with the hexagonal habits of the polyamide homopolymer, whereas variable‐temperature WAXD data suggested that upon heating from ambient, a melt‐crystallized copolymer might exhibit so‐called Brill transition before complete melting. Based on various DSC and variable‐temperature WAXD experimental results obtained in this study, the applicability of different melting mechanisms that might be responsible for multiple melting characteristics of various crystallized PEBA copolymer samples were discussed. It was postulated that the low (T m1) endotherm was primarily because of the disruption of less thermally stable, short‐range ordered structure of amorphous polyamide segments of the copolymer, which was only formed after the completion of primary crystallization via so‐called annealing effects. The intermediate (Tm2) and high (Tm3) endotherms were attributed to the melting of primary crystals within polyamide crystalline microdomains of the copolymer. The appearance of these two melting endotherms might be somehow complicated by thermally induced Brill transition. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2035–2046, 2008