Effect of Aliphatic Diacid Chain Length on Properties of Semiaromatic

Article Cite This: Ind. Eng. Chem. Res. 2019, 58, 7217−7226

pubs.acs.org/IECR

Effect of Aliphatic Diacid Chain Length on Properties of Semiaromatic Copolyamides Based on PA10T and Their Theoretical Study Wutong Feng,†,‡,§,# Guangji Zou,†,§,# Yue Ding,†,§,# Tianhao Ai,†,§ Pingli Wang,*,† Zhonglai Ren,† and Junhui Ji*,†

Ind. Eng. Chem. Res. 2019.58:7217-7226. Downloaded from pubs.acs.org by UNIV OF ROCHESTER on 05/09/19. For personal use only.

†

National Engineering Research Center of Engineering Plastics, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China ‡ Shandong Provincial Key Laboratory for Special Silicon-Containing Materials, Advanced Materials Institute, Qilu University of Technology (Shandong Academy of Sciences), Jinan 250014, China § University of Chinese Academy of Sciences, Beijing 100049, China S Supporting Information *

ABSTRACT: A series of 10T/10X (X = 6, 8, 10, 12, 14, 16) copolyamides was synthesized, and the thermal and mechanical properties were investigated. The effects of the lengths of alkyl chains of diacids on their resultant properties were studied, and we found that the introduction of a small amount of aliphatic diacid hardly changed the lattice parameters of the copolyamides. The Tm and Tc values of the 10T/10X copolyamides decreased and had a zigzag oscillation behavior as the lengths of alkyl chains on the diacids increased. A density functional theory study showed that the observed behaviors were related to the change in hydrogen bond strength and the length mismatches of the diacids in the copolymer chains. The tensile strength decreased slightly, while the elongation at break increased significantly with an increase in the chain length of the aliphatic diacid; further, the notched impact strength decreased but was still higher than PA10T.

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INTRODUCTION With the current increase in combustion temperature of automotive engine fuel and the wide use of surface mount technology (SMT), traditional nylons such as polycaprolactam (PA6)1 and poly(hexamethylene hexanediamide) (PA66)2 have not been able to satisfy SMT requirements, and semiaromatic nylons or fully aromatic polyamides are gaining more and more attention due to their excellent heat-resistant properties. Among them, semi-aromatic nylons show great potential because they possess the superb rigidity and heatresistant properties of fully aromatic polyamides and the desirable melt processing properties of aliphatic polyamides. At present, the main varieties of heat-resistant semi-aromatic nylons based on terephthalic acid are poly(tetramethylene terephthalamide) (PA4T),3 poly(pentamethylene terephthalamide) (PA5T), poly(hexamethylene terephthalamide) (PA6T),4 poly(nonamethylene terephthalamide) (PA9T),5 poly(decamethylene terephthalamide) (PA10T),6,7 and poly(dodecamethylene terephthalamide) (PA12T).8 Often singlecomponent polymers cannot meet the application requirements for their target markets; e.g., the melting points of pure PA4T and PA6T are 430 and 370 °C,9 respectively, which are higher than their decomposition temperatures which does not allow them to be melt processed. In addition, some semiaromatic nylons, like PA9T, PA10T, and PA11T, have poor © 2019 American Chemical Society

impact toughness, which severely limits their application in some special fields. Therefore, commercially available semiaromatic polyamides are different copolymerized or blended modified varieties with excellent resulting performances, e.g., Dupont ZYTELHTN (PA6T/66, PA6T/66/6I), BASF Ultramid (PA6T/6), EMS Grivory (PA6T/66, PA6T/6I, 10T/X), and Arkema Rilsan (10T/X).10 Compared with blended modifications, copolymerization is the more fundamental method, which adjusts the comprehensive properties of the material based on their chemical structure.11−14 First, the properties of the comonomer units will be reflected in the properties of final copolymers due to the differences in their chemical structures. Second, the addition of comonomers will disturb the regular distribution in a homopolymer, which will affect the crystallization behavior of materials because of physical structure difference. Finally, whether the chosen comonomer is close in physical structure to the main monomer or not will also affect the final performance of the material based on the structure and energy optimization. Therefore, much research has been performed Received: Revised: Accepted: Published: 7217

February 22, 2019 April 9, 2019 April 12, 2019 April 12, 2019 DOI: 10.1021/acs.iecr.9b01041 Ind. Eng. Chem. Res. 2019, 58, 7217−7226

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Industrial & Engineering Chemistry Research Scheme 1. Synthesis Route of 10T/10X Copolyamidesa

a

m and n are variables.

significance for the future development of heat-resistant semiaromatic copolyamides based on PA10T.

based on the modification of semi-aromatic nylons. Novitsky et al. 15 prepared a series of 10T-co-6T and 12T-co-6T copolyterephthalamides to reveal eutectic melting behavior. Cakir et al.16 obtained PA6/Dytek A-IPA block copolyamides with different melting points and crystallization temperatures through solid-state polycondensation (SSP) of PA6 and a nylon salt of 1,5-diamino-2-methylpentane (Dytek A) and isophthalic acid (IPA). Rwei et al.17 studied the crystallization kinetics of PA66/6T, proving that PA66 and PA6T are isomorphous, and the melting points of PA66/6T(5%−30%) ranged from 262 to 272 °C, which were greatly reduced from the melting point of their PA6T (370 °C) counterpart. Thus, it can be seen that most of the work is focused on the influence of one or two comonomers on the chemical structure and physical properties of semi-aromatic polyamides. The mechanism of influence of a series of comonomers on the properties of the resulting semi-aromatic polyamides is instructive for the design of new copolymers of semi-aromatic polyamides. In this article, we focus on the effect of a series of aliphatic diacids with different alkyl chain lengths on the properties of semi-aromatic copolyamide, and the mechanism is attempted to be understood. One of the monomers, 1,10-decanediamine (DMD), is a biomass derived from castor oil, and as a result, PA10T is a highlighted material that has good heat resistance, dimensional stability, and melt processability.6 PA10T is used as a structural template for the copolymerization with different aliphatic diacids. Moreover, in our previous work, we introduced different amounts of dodecanedioic acid6 and 1,12-dodecanedicarboxylic acid7 into PA10T and found that the elongation at break was significantly improved by the introduction of long chain aliphatic acids, which showed that the different lengths of aliphatic diacid chains can induce different properties in the resulting copolyamides. Therefore, a series of linear aliphatic diacids (adipic acid, suberic acid, decanedioic acid, dodecanedioic acid, 1,12-dodecanedicarboxylic acid, and 1,14-tetradecanedicarboxylic acid) will be copolymerized with PA10T, as well as different PA10T/10X (X = 6, 8, 10, 12, 14, or 16, where X refers to the number of carbon atoms in the aliphatic diacids) will be synthesized by prepolymerization and solid-state polycondensation. The effect of the aliphatic diacid length on the performances of semiaromatic copolyamides based on PA10T was studied by analyzing the structure, composition, and thermal and mechanical properties. Furthermore, we used density functional theory (DFT) to help interpret the experimental results. As a powerful tool for the simulation of physical, chemical, and material systems, DFT was used to analyze the difference in chemical structure originating from different aliphatic diacids. Taking less computational efforts compared with the wave function methods (e.g., second-order Møller−Plesset perturbation theory (MP2)),18 DFT methods have proved able to sufficiently characterize weak interactions.19−24 We found that M06-2X performed very well when dealing with hydrogen bond energy in these complexes.25,26 The work will have

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EXPERIMENTAL SECTION

Materials. 1,10-Diaminodecane (DMD) was purchased from Wuxi Yinda Co., Ltd. Terephthalic acid (TPA) was purchased from Jinan Mingxin Chemical Co., Ltd. Adipic acid, suberic acid, decanedioic acid, and dodecanedioic acid were purchased from Aladdin Industrial Corporation. 1,12-Dodecanedicarboxylic acid and 1,14-tetradecanedicarboxylic acid were purchased from the Wuhan Yuancheng Group. Benzoic acid (BA), sodium hypophosphite (SHP), and 1,1,1,3,3,3hexafluoro-2-propanol (HFIP) were purchased from Shanghai Macklin Biochemical Co., Ltd. Concentrated sulfuric acid (96%) and N,N-dimethylformamide (DMF) were purchased from Beijing Chemical Reagent Company. Synthesis of 10T/10X Prepolymers. 10T/10X copolyamides were synthesized from their corresponding aliphatic diacids, terephthalic acid, and 1,10-diaminodecane by a polycondensation reaction as shown in Scheme 1. An autoclave was charged with aliphatic diacid (adipic acid, suberic acid, decanedioic acid, dodecanedioic acid, 1,12-dodecanedicarboxylic acid, or 1,14-tetradecanedicarboxylic acid, 0.10 mol), terephthalic acid (0.90 mol), 1,10-diaminodecane (1.01 mol), benzoic acid (0.03 mol), sodium hypophosphite (0.1 wt %), and deionized water (150 wt %). The mixture was stirred at a rate of 50 rpm to form a slurry under a N2 atmosphere. Then, the slurry was heated to 80 °C and kept at 80 °C for 60 min and subsequently heated to 235 °C and kept at 235 °C for 60 min. During the heating process, the steam was discharged to keep the pressure between 2 and 3 MPa. After that, the remaining steam was removed to fully relieve the pressure within 60 min. White solid prepolymers were acquired once the temperature reached room temperature. Solid-State Polycondensation (SSP). The 10T/10X prepolymers were smashed into fine particles and placed in a vacuum dryer to increase the molecular weight. The pressure in the vacuum dryer was reduced to 30 Pa. Then, the 10T/10X prepolymers were heated to 270 °C, and the temperature was maintained for about 5 h. The 10T/10X copolyamides were obtained after the vacuum dryer naturally cooled to room temperature. The resultant products were washed with DMF and deionized water several times and dried for storage. Computational Method. Full geometric optimization of the constitutional units 10T and 10X, hydrogen bonded complexes, and frontier orbitals were carried out using density functional theory (DFT). The functional M06-2X27,28 was chosen to describe the weak interaction. Hydrogen bond needs a large space occupation; thus, diffusion and polarization basis functions 6-31+g(d,p) were applied for a better description of the geometrical optimization and the frontier orbitals. In calculating the interaction energy in the hydrogen bonded complexes, the binding energies were corrected by the basis set superposition errors (BSSE) using the counterpoise method.29 7218

DOI: 10.1021/acs.iecr.9b01041 Ind. Eng. Chem. Res. 2019, 58, 7217−7226

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Industrial & Engineering Chemistry Research The Monte Carlo (MC) algorithm was also used to estimate the volume of the complexes. All these calculations were performed using the Gaussian 09 program.30 Characterization. Size exclusion chromatography (SEC) analyses were performed on an Agilent Technologies 1260 Infinity II instrument using HFIP as the mobile phase. The injection volume was 100 μL, and the flow rate was 1.0 mL/ min. The standard sample used was poly(methyl methacrylate) (PMMA). The intrinsic viscosity of the resultant samples was measured using an Ubbelohde viscometer in a water bath at 25.00 ± 0.05 °C. The efflux time of 96% concentrated sulfuric acid and the sulfuric acid solution of the samples are recorded as t0 and t1, respectively. The intrinsic viscosity, recorded as [η], was calculated by the Solomon and Ciuta relationship:31 [η ] =

Table 1. Molecular Weight of PA10T and 10T/10X Copolyamides Mwa (g/mol)

PDIa

[η]b (dL/g)

Mnb (g/mol)

S-0 S-1 S-2 S-3 S-4 S-5 S-6

6395 6794 6884 6724 6853 5881 6275

22,935 23,051 24,262 23,118 24,293 17,471 23,287

3.586 3.393 3.524 3.438 3.545 2.971 3.711

1.06 1.09 1.14 1.08 1.18 1.15 1.17

11,162 11,553 12,211 11,423 12,742 12,343 12,609

Obtained by size exclusion chromatography (SEC). bObtained by viscosity tests.

PA10T/10X was determined to be about 6000 g/mol according to SEC results. The molecular weight obtained by the viscosity method is different from that obtained by SEC. Nevertheless, the above results confirmed that semi-aromatic polyamides can be effectively synthesized by prepolymerization and solid-state polycondensation, and the molecular weights of PA10T/10X were similar. This means that in subsequent discussion the performance differences with respect to molecular weight should be negligible. FTIR spectra of 10T/10X copolyamides are shown in Figure 1. All the characteristic bands of the methylene and amide

(1)

where c (concentration of sulfuric acid solution) is 0.005 g/ mL, ηsp (specific viscosity) can be calculated by (t1/t0 −1), and ηr (relative viscosity) can be obtained by t1/t0. Equation 2 was used to estimate Mn of PA10T and 10T/10X copolyamides.15 [η] = 0.000558(dL/g)M n 0.81

Mna (g/mol)

a

2(ηsp − ln ηr ) c

Samples

(2)

The FTIR spectra were collected between 4000 and 600 cm−1 on a JASCO FT/IR-6800 instrument with a resolution of 2.0 cm−1. The 1H NMR spectra were obtained on a BRUKER AVANCE II-400 apparatus using trifluoroacetic acid-D (CF3COOD) as the solvent. X-ray diffraction patterns were obtained employing a Bruker D8 focus diffractometer and using a Cu Kα (λ = 0.154 nm) radiation source with an increment of 0.02° at a scan speed of 0.1 s/step in 2θ range of 5° to 65°. Differential Scanning Calorimeter (DSC) thermal analyses were carried out on a METTLER DSC1 differential scanning calorimeter under a nitrogen flow of 50 mL/min. Samples of about 5 mg were heated to 340 °C to eliminate any thermal history and kept at 340 °C for 5 min. Then, the samples were cooled to 0 °C and were subsequently heated to 340 °C again at a rate of 10 °C/min. Dynamic mechanical analysis was performed on a METTLER DMA/SDTA 861e apparatus. The samples of 18 mm × 4.5 mm × 1 mm were prepared by injection molding with HAAKE MiniJet Pro. Data were collected from −30 to 200 °C at a heating rate of 3 °C/min in the tension mode at 1 Hz. All samples for mechanical tests were prepared by injection molding with a HAAKE MiniJet Pro. Tensile strength and elongation at break were measured on an INSTRON-5699 instrument at a stretching rate of 5 mm/min according to ISO 527-2:1993. Five parallel experiments were done for each sample at room temperature. Notched impact strength was measured with a Wuzhong Material Tester XJ-300A according to ISO 179−1:2000 and three parallel experiments were done for each sample at room temperature.

Figure 1. FTIR spectra of PA10T and 10T/10X copolyamides.

groups are as follows: 3307 cm−1 (hydrogen bond and N−H stretching vibration), 3065 cm−1 (combination of C−N stretching vibration and N−H stretching vibration), 2922 cm−1 (C−H stretching vibration and N−H in-plane bending vibration), 2851 cm−1 (C−H stretching vibration), 1623 cm−1 (C = O stretching vibration), 1537 cm−1 (C−N stretching vibration and N−H bending vibration), 1495 cm−1 (C−N stretching vibration and C−H bending vibration), 1288 cm−1 (C−CO stretching vibration), 862 cm−1 (C−H vibration in benzene ring), and 639 cm−1 (N−H bending vibration). It is clear that the chemical structure of 10T/10X copolyamides and PA10T are similar. The observed bands in the FTIR spectra are consistent with those previously reported6,7 and indicate that the target copolyamides were successfully synthesized.

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RESULTS AND DISCUSSION We synthesized polymers PA10T, PA10T/106, PA10T/108, PA10T/1010, PA10T/1012, PA10T/1014, and PA10T/1016, herein referred to as S-0, S-1, S-2, S-3, S-4, S-5, and S-6, respectively. Table 1 summarizes the characteristics of PA10T/ 10X, and the number-average molecular weight (Mn) of 7219


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H NMR spectroscopy is an important means to analyze the copolymer chemical structure and composition. The 1H NMR spectra of PA10T and 10T/10X copolyamides are shown in Figure 2. The solvent used in the tests is trifluoroacetic acid-D,

Figure 3. XRD curves of PA10T and 10T/10X copolyamides.

It is well known that the properties of polymers are closely related to the chemical structure; this is the case for polyamides, where the density of amide bonds and the intermolecular or intramolecular hydrogen bonds are key factors to affecting the properties of polyamides. To better understand the relationship between the chemical structure of PA10T/10X and their properties, DFT calculations were performed considering full geometry optimization of the constitutional units 10T and 10X, hydrogen bonded complexes, and frontier orbitals. The crystal lattice model was not used because it was unsuitable for polymers as the chain must be entangled with each other instead of in a stratified arrangement. For simplicity, we analyzed the constitutional units 10T and 10X using −CH3 as the linking group, and all geometric configurations were fully optimized. As shown in Figure 4, it was clear that two or three hydrogen bonds formed in each dimer, while different degrees of distortion were found in a variety of structures, which is due to the mismatch of the length of aliphatic diacid with that of terephthalic acid in the 10T segments. The hydrogen bond properties were determined by its HOMO and LUMO orbitals, e.g., the 106 segment, as shown in Figure S2 of the Supporting Information. The length of the hydrogen bond was not so far distinct among those dimers (approximately 1.9−2.0 Å), and even so, the bond length indicated that the hydrogen bonds existing in those polymers were strong. The binding energy (Ebinding) was calculated from the following equation:

Figure 2. 1H NMR spectra of PA10T and 10T/10X copolyamides.

and the chemical shifts corresponding to the solvent peaks are present at 11.63 and 2.37 ppm, as shown in Figure S1 of the Supporting Information. For PA10T (S-0), the peaks at 1.61, 2.00, 3.88, and 8.15 ppm belong to the proton signals at positions a, b, c, and T, respectively. The integration area calculation revealed the integral area ratio of δa, δb, δc, and δT is close to 3:1:1:1, which agrees with the expected molecular structure of PA10T. When different aliphatic diacids were copolymerized with PA10T, new peaks at 2.96−2.99 ppm appeared, which were attributed to the CH2 of the aliphatic diacid attached to the amide groups. Although the alkyl length of the aliphatic diacid is differed, it had no significant effect on the chemical environment of the characteristic protons. As a result, the peak positions of PA10T/10X were similar. As presented in Table S1 of the Supporting Information, the 10X segments mole content of 10T/10X copolyamides were calculated by δd/δc, δe/δc, δf/δc, δg/δc, δh/δc, and δi/δc, and these values were 11%, 11%, 10%, 10%, 10%, and 10%, respectively, which agreed well with the contents of 10T/106, 10T/108, 10T/1010, 10T/1012, 10T/1014, and 10T/1016 copolyamides in feed ratio. X-ray diffraction patterns can be used to study the crystal structure and crystallization of the resultant copolymers. As shown in Figure 3, all XRD curves showed three distinct peaks at (2θ)1, (2θ)2, and (2θ)3. These diffraction peaks of 10T/10X copolyamides were at similar positions with PA10T, which indicated that the incorporation of the aliphatic diacids did not change the crystal structure of PA10T. However, as the length of the aliphatic diacid increased, peaks associated with 10T/ 10X copolyamides became wider, indicating that the crystallinity of the materials decreased.

E binding = E10T/10X − E10T − E10X

(3)

with BSSE correction of the dimer indicating the hydrogen bond strength in the dimer. The volume (V) of the dimer was very interesting due to the high torsion of those two chains. It is reasonable to define the density of hydrogen bond energy (DHBE) as the negative value of the binding energy per volume with the following equation: DHBE = −E binding /V

(4)

so that we can analysis the synergistic effect of the two factors and investigate the strength of hydrogen bond in the entire polymers. For all samples, Ebinding, V, and DHBE are listed in Table 2. For PA10T, the Ebinding was −32.30 kcal/mol, and there were only two hydrogen bonds in each 10T−10T unit 7220


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Figure 4. Optimized structures of (a) 10T−10T unit dimer and 10T−10X unit dimer: (b) X = 6, (c) X = 8, (d) X = 10, (e) X = 12, (f) X = 14, and (g) X = 16. Hydrogen bond lengths (Å) are marked. For clarity, the C atom in the 10X chain is highlighted with a yellow color.

Table 2. Ebinding, V, and DHBE of 10T/10X Dimers Ebinding (kcal/mol) V (cm3/mol) DHBE(kcal/cm3)

S-0

S-1

S-2

S-3

S-4

S-5

S-6

−32.30 542.471 0.05954

−30.36 578.386 0.05249

−28.77 569.282 0.05054

−30.08 589.017 0.05107

−30.26 665.418 0.04548

−29.20 628.933 0.04643

−29.72 717.526 0.04142

Table 3. Thermal Properties of 10T/10X Copolyamides Samples

S-0

S-1

S-2

S-3

S-4

S-5

S-6

Tm1 (°C)a Tm2 (°C)a ΔHm1 (J/g)a ΔHm2 (J/g)a ΔHm (J/g)a Tc (°C)a ΔHc (J/g)a Tg (°C)b

313.18 302.80 −39.08 −61.23 −100.31 287.73 44.58 132.31

306.28 295.66 −34.75 −50.60 −85.35 281.87 45.42 116.01

303.94 293.50 −20.65 −56.80 −77.45 278.35 50.35 111.53

305.36 294.13 −22.65 −46.30 −68.95 279.25 49.46 110.50

302.70 292.89 −17.42 −53.89 −71.31 276.85 50.60 110.23

303.25 293.97 −14.79 −50.04 −64.83 278.83 46.31 111.21

302.91 292.51 −18.39 −39.43 −57.82 277.94 44.09 99.34

a

Obtained by DSC. bObtained by DMA.

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lecular hydrogen bonding; therefore, the ΔHm values of 10T/ 10X copolyamides decreased with an increase in the length of aliphatic diacid carbon chains. More importantly, DHBE had a similar decrease in Tm or Tc values accompanied by a zigzag oscillation behavior as the length of the alkyl chain of aliphatic diacid increased, which indicated that the hydrogen bond density is one of the most important factors as the strength of hydrogen bonds of PA10T/10X are roughly the same. Ultimately, both the polymer chain flexibility and the hydrogen bonding effect determined the thermal properties of PA10T/ 10X. Glass transition is a phenomenon related to molecular motion, which is related to molecular geometry, flexibility, and intermolecular forces in a polymer. As presented in Table 3, the glass transition temperature (Tg) of PA10T was 132.31 °C, while the Tg values were 116.01, 111.53, 110.50, 110.23, 111.21, and 99.34 °C for 10T/10X copolyamides with X = 6, 8, 10, 12, 14, 16, respectively. Although the Tg values of the 10T/10X copolyamides decreased to different extents, they are still much higher than the aliphatic polyamides, such as PA6 (60 °C),37 PA66 (65 °C),37 PA1016 (45 °C),38 and PA1020 (45.9 °C).39 The Tg values of all 10T/10X copolyamides were lower than PA10T, which was attributed to the reduction in rigid benzene rings present and the density of the hydrogen bonds. The 10T/10X polyamides had more flexible aliphatic chains than PA10T, resulting in higher flexibility of the molecular chains. The Tg values of the 10T/10X copolyamides decreased with an increase in the length of aliphatic diacid carbon chains, which was mainly due to an increase in molecular chain flexibility. Further, the hydrogen bond density of 10T/10X polyamides decreased with an increase in the length of aliphatic diacid chains, which also contributed to the reduction in Tg. In addition, it is precisely because the Tg value reflects the transformation of the amorphous part of the material from freezing to motion that a higher crystallinity leads to a higher Tg. Assuming that the ΔHm,100% value of PA10T/10X is the same as that of PA10T, the crystallinity of PA10T/10X nearly decreased with an increase in the length of aliphatic diacid chains, based on the ΔHm. The smaller the crystallinity is, the looser the polymer chains stack is and the higher the activity of the molecular chains is, which also leads to a decrease in the Tg. It can be seen from the above studies that the thermal properties of PA10T are affected by copolymerization. Compared to aliphatic polyamides, do the thermal properties of semi-aromatic polyamides modified by copolymerization still have advantages? In order to answer this question, we have made a comprehensive comparison of the verifiable polyamide varieties according to the change in Tm and Tg values, as shown in Figure 6. By comparing the Tm and Tg values of PA10T, PA11T, PA12T, and PA13T, it is obvious that the Tm and Tg values of semi-aromatic polyamides based on terephthalic acid decreased with an increase in the length of aliphatic diamine chains.40 In addition, comparing the Tm and Tg values of 6,T6,6 copolyamides with PA6T and PA66 also proves that the copolymerization of aliphatic polyamides with semi-aromatic polyamides can affect their properties to obtain new materials with high melting point and good processability. Although copolymerization with different aliphatic diacids can reduce the Tm and Tg values of PA10T, PA10T/10X still exhibits desirable thermal properties compared with most aliphatic polyamides. As shown in Figure S4 of the Supporting Information, the

dimer as presented in Figure 4(a). Therefore, the average bond energy per hydrogen bond was about 16.15 kcal/mol. However, the Ebinding of the 10T−10X unit dimers was from −30.36 to −28.77 kcal/mol, and there were three hydrogen bonds in each 10T−10X unit dimer. Therefore, the average bond energy per hydrogen bond was about 9.59 to 10.12 kcal/ mol, which is much less than PA10T. It can be seen that the hydrogen bonding interaction between the 10T unit and the 10T unit was much higher than the hydrogen bonding interaction between the 10T unit and the 10X unit. Also, DHBE decreased relative to an accompanying zigzag oscillation behavior as the alkyl chain length of the aliphatic diacid increased. The difference in hydrogen bonding interactions will affect the properties of materials and is discussed in the following sections. The thermal properties of PA10T/10X were determined by DSC and DMA measurements, as shown in Table 3. The melting peaks showed distinct double-melting endotherms (as presented in Figure S3 of the Supporting Information), which often occur in other semi-aromatic polyamides such as PA4T and PA6T.32,33 The double-melting endotherm is a common phenomenon in many crystalline polymers like polyethylene terephthalate (PET),34 polypropylene (PP),35 and polyamide (PA),14 which is due to the melting, recrystallization and remelting behavior of the initial crystals during the second heating stage.36 The Tm values corresponding to the peaks in the high and low temperature zones were defined as Tm1 and Tm2, respectively. A decrease was seen relative to an accompanying zigzag oscillation behavior corresponding to an increase in the alkyl chain length of the aliphatic diacids chains (Figure 5) as well as the melting enthalpy (ΔHm).

Figure 5. Relationship between Tm, Tc, and DHBE of the samples.

Overall, all Tm1 and Tm2 values of 10T/10X copolymers were smaller than that of PA10T because some 10T segments were replaced by 10X segments, and the carbon chain was more flexible than a benzene ring, which led to an increase in melting entropy and a reduction in Tm. Second, as mentioned above, for the strong polarity of the amide bonds, the formation of hydrogen bonds strongly influence the polyamides performance. The existence of hydrogen bonds in the fusant will further limit the appearance of many possible conformations, thus reducing the melting entropy and increasing the melting point. For 10T/10X copolyamides, the amide bond density of the polymer chain decreased with an increase in the aliphatic diacid carbon chains, resulting in a weakening of intermo7222


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another chain. For polyamide, the effect of amide bond density on tensile strength had a certain regularity, which caused the tensile strength to decrease with a decrease in the density of amide bonds. For 10T/10X copolyamides, the amide bond density and hydrogen bond density decreased with an increase in the length of aliphatic diacid chains; thus, the tensile strengths of 10T/10X copolyamides showed a downward trend. Although the tensile strengths of 10T/10X copolyamides decreased in varying degrees, they were still much higher than those of some common nylons like PA6 (69.7 MPa), PA11 (41.3 MPa), and PA12 (40.9 MPa).52 In addition, the crystallinity also has a certain effect on the tensile strength and modulus, and increasing crystallinity is beneficial to an increase in tensile strength and modulus. DSC results showed that the crystallinity of the samples decreased with an increase in the length of the aliphatic diacid chains, which also promoted a decrease in tensile strength and modulus. The elongation at break of PA10T was 35.41%, while the tensile properties of 10T/10X copolyamides were 141.50%, 227.35%, 237.43%, 243.23%, 249.07%, and 256.77% for copolymers with X = 6, 8, 10, 12, 14, 16, respectively. It can be concluded that the elongations at break of 10T/10X copolyamides are increased with an increase in the length of aliphatic diacid chains. Also, the copolymers exhibited a higher elongation at break because of the flexibility of the molecular chain was increased upon increasing the length of the aliphatic diacid chains. The impact strength is an important determinant of the toughness and is defined as the energy absorbed per unit crosssectional area when the specimen is broken or cracked under impact load. As shown in Figure 7(b), the notched impact strengths of 10T/10X copolyamides were 23.23, 21.56, 19.48, 18.13, 17.19, and 16.67 kJ/m2 for copolymers with X = 6, 8, 10, 12, 14, 16, respectively, which were higher than PA10T whose notched impact strength was 13.85 kJ/m2, while the notched impact strengths of 10T/10X copolyamides decreased with an increase in the length of aliphatic diacid chains due to the rigidity and flexibility of the materials. The fracture of materials consisted of three parts: crack initiation, crack development, and fracture initiation. For 10T/10X copolyamides, the rigidity of the molecular chains decreased with an increase in the length of aliphatic diacid chains because of the reduction of the relative content of rigid benzene rings, resulting in the reduction of the energy for crack initiation.

Figure 6. Comparison of Tm and T g values for 10T/10X copolyamides with other common aliphatic, semi-aromatic, and aromatic nylons.4,37−51

results from TGA also confirmed that 10T/10X copolyamides had excellent thermal stability. The mechanical properties of PA10T and 10T/10X copolyamides are shown in Figure 7 and Table S2 of the Supporting Information. From the stress−strain curve, it can be clearly seen that the tensile behavior of all PA10T and 10T/ 10X copolyamides can be divided into elastic deformation, yield, development of large deformation, and strain hardening stages. Also, all the samples showed an obvious ductile fracture phenomenon. Figure 7(b) shows the relationship between the tensile strength and elongation at break of the samples. The tensile strength decreased, and the elongation at break increased significantly with an increase in the length of aliphatic diacid chains. PA10T had a high tensile strength of 86.00 MPa, while the tensile strengths of the 10T/10X copolyamides were 74.40, 73.56, 72.96, 72.64, 72.05, and 72.20 MPa for copolymers with X = 6, 8, 10, 12, 14, 16, respectively. The polyamide was linked by many repetitive structural units through amide bonds that had specific polarity, and the hydrogen from the amide bond in each chain can form a strong hydrogen bond with a carbonyl group of an amide bond in

Figure 7. Mechanical properties of 10T/10X copolyamides: (a) stress−strain curves, (b) relationship between the tensile strength, elongation at break, and notched impact strength of the samples. 7223


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Industrial & Engineering Chemistry Research However, with an increase in the length of aliphatic diacid chains, the flexibility of the copolymer molecular chains increased, the free volume increased, and the mobility of molecular chains increased, leading to a greater difficulty for crack development and a higher energy absorbed by the material under impact load. For 10T/10X copolyamides, the effect of rigidity reduction on impact strength was greater than that of the flexibility increase, so the notched impact strength of 10T/10X copolyamides showed a decreasing trend.

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AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected]. *E-mail: [email protected].

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ORCID

CONCLUSION A series of 10T/10X (X = 6, 8, 10, 12, 14, 16) copolyamides have been successfully synthesized by prepolymerization and solid-state polycondensation, which were derived from 1,10diaminodecane, terephthalic acid, and linear aliphatic diacids in deionized water. XRD showed the introduction of a slight aliphatic diacid had little effect on the crystal structure. The Tm and Tc values obtained by DSC showed that all Tm and Tc values of 10T/10X copolyamides were slightly lower than PA10T, as well as an interesting oscillation phenomenon observed in the sequence as X increased. The DFT calculations can explain the high Tm and Tc values as well as the oscillation behavior appearing in the copolymer series. The binding energy of each dimer was calculated to determine the strength of hydrogen bonds between the 10T and 10X segments. The oscillating behavior in the binding energy satisfied the experimental results, and the change of DHBE among various dimers presented a clear relationship between the copolymers and the length of aliphatic diacid chains. The Tg value obtained by DMA and the Tg value of 10T/10X copolyamides decreased with an increase in the length of aliphatic diacid chains, which was related to the higher flexibility of molecular chains and a decrease in the crystallinity. For mechanical properties, even though the tensile strength of 10T/10X was slightly less than PA10T, 10T/10X polyamides still possessed a much higher tensile strength than some of the more common nylons. The elongation at break increased significantly with an increase in the length of aliphatic diacid chains, and the notched impact strength decreased but was still greater than PA10T. Both experimental studies and theoretical simulation revealed that the properties of 10T/10X polyamides are strongly affected by the binding energy between dimers as well as the densities of hydrogen bonds in the whole of the polymers. The series of copolymers 10T/10X has superior mechanical properties, such as elongation at break and impact strength, without sacrificing too much tensile strength, while also keeping a relatively high thermal stability. This gives 10T/ 10X copolyamides a potential value for the application in many fields. In conclusion, the results discussed herein shall be of significant value for guiding the direction of future researchers in the development of heat-resistant semi-aromatic copolyamides for various applications.

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PA10T and 10T/10X copolyamides (Figure S4), and mechanical properties of PA10T and 10T/10X copolyamides (Table S2). (PDF)

Pingli Wang: 0000-0002-6539-4368 Author Contributions #

Wutong Feng, Guangji Zou, and Yue Ding contributed equally to this work. Funding

This work was financially supported by the National Natural Science Foundation of China (Grant 51473175) and the Opening Topic Fund (2017−4) of Shandong Provincial Key Laboratory for Special Silicon-Containing Materials. Notes

The authors declare no competing financial interest.

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REFERENCES

(1) Liu, Z. G.; Deng, Y. J.; Han, Y.; Chen, M.; Sun, S. L.; Cao, C. L.; Zhou, C.; Zhang, H. X. Toughening of Polyamide-6 with a Maleic Anhydride Functionalized Acrylonitrile-Styrene-Butyl Acrylate Copolymer. Ind. Eng. Chem. Res. 2012, 51, 9235−9240. (2) Li, X. Y.; Gu, X. Y.; Zhang, S.; Li, H. F.; Feng, Q. L.; Sun, J.; Zhao, Q. Improving the Fire Performance of Nylon 6,6 Fabric by Chemical Grafting with Acrylamide. Ind. Eng. Chem. Res. 2013, 52, 2290−2296. (3) Papaspyrides, C. D.; Porfyris, A. D.; Vouyiouka, S.; Rulkens, R.; Grolman, E.; Poel, G. V. Solid State Polymerization in a MicroReactor: The Case of Poly(Tetramethylene Terephthalamide). J. Appl. Polym. Sci. 2016, 133, n/a. (4) Lee, M.; Son, K.; Kim, J.; Kim, D.; Min, B. H.; Kim, J. H. Effect of PA6T on Morphology and Electrical Conductivity in PA66/PA6T/ PPE/Multiwalled Carbon Nanotube Nanocomposites. Compos. Sci. Technol. 2018, 164, 260−266. (5) Yamamoto, H.; Tashiro, K.; Ishino, K.; Takahashi, M.; Endo, R.; Asada, M.; Li, Y. Q.; Katsube, K.; Ishii, T. Crystal Structures and Phase Transition Behavior of Poly(Nonamethylene Terephthalamide) and Its Model Compounds. Polymer 2017, 116, 378−394. (6) Zou, G. J.; Wang, P. L.; Feng, W. T.; Ren, Z. L.; Ji, J. H. Poly(Decamethylene Terephthalamide) Copolymerized with LongChain Alkyl Dodecanedioic Acid: Toward Bio-Based Polymer and Improved Performances. J. Appl. Polym. Sci. 2018, 135, 46531. (7) Feng, W. T.; Wang, P. L.; Zou, G. J.; Ren, Z. L.; Ji, J. H. Synthesis and Characterization of Semiaromatic Copolyamide 10T/ 1014 with High Performance and Flexibility. Des. Monomers Polym. 2018, 21, 33−42. (8) Liu, M. Y.; Li, K. F.; Yang, S. H.; Fu, P.; Wang, Y. D.; Zhao, Q. X. Synthesis and Thermal Decomposition of Poly(Dodecamethylene Terephthalamide). J. Appl. Polym. Sci. 2011, 122, 3369−3376. (9) Shashoua, V. E.; Eareckson, W. M. Interfacial Polycondensation 0.5. Polyterephthalamides from Short-Chain Aliphatic, Primary, and Secondary Diamines. J. Polym. Sci. 1959, 40, 343−358. (10) Zhang, C. H. Progress in Semicrystalline Heat-Resistant Polyamides. e-Polym. 2018, 18, 373−408. (11) Wang, L. L.; Dong, X.; Huang, M. M.; Muller, A. J.; Wang, D. J. Self-Associated Polyamide Alloys with Tailored Polymorphism Transition and Lamellar Thickening for Advanced Mechanical Application. ACS Appl. Mater. Interfaces 2017, 9, 19238−19247. (12) Wang, D.; Feng, L. F.; Gu, X. P.; Wang, J. J.; Zhang, C. L.; He, A. H. Synergetic Effect of a Reactive Compatibilizer and OMMT on

ASSOCIATED CONTENT

* Supporting Information S

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.iecr.9b01041. 1

H NMR spectra of trifluoroacetic acid-D (Figure S1), H NMR integral data of 10T/10X copolyamides (Table S1), HOMO and LUMO for 10T−106 unit dimers (Figure S2), DSC curves of PA10T and 10T/10X copolyamides (Figure S3), TGA and DTG curves of 1

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Article

Industrial & Engineering Chemistry Research the Dispersion of PA6/PDMS Blend with a High Viscosity Ratio. Ind. Eng. Chem. Res. 2019, 58, 3714−3720. (13) Ren, D. W.; Tu, Z. K.; Yu, C. J.; Shi, H. C.; Jiang, T.; Yang, Y. K.; Shi, D.; Yin, J. H.; Mai, Y. W.; Li, R. K. Y. Effect of Dual Reactive Compatibilizers on the Formation of Co-Continuous Morphology of Low Density Polyethylene/Polyamide 6 Blends with Low Polyamide 6 Content. Ind. Eng. Chem. Res. 2016, 55, 4515−4525. (14) Tang, J.; Xu, B. W.; Xi, Z. H.; Pan, X.; Zhao, L. Controllable Crystallization Behavior of Nylon-6/66 Copolymers Based on Regulating Sequence Distribution. Ind. Eng. Chem. Res. 2018, 57, 15008−15019. (15) Novitsky, T. F.; Lange, C. A.; Mathias, L. J.; Osborn, S.; Ayotte, R.; Manning, S. Eutectic Melting Behavior of Polyamide 10,T-Co-6,T and 12,T-Co-6,T Copolyterephthalamides. Polymer 2010, 51, 2417− 2425. (16) Cakir, S.; Nieuwenhuizen, M.; Janssen, P. G. A.; Rulkens, R.; Koning, C. E. Incorporation of a Semi-Aromatic Nylon Salt into Polyamide 6 by Solid-State or Melt Polymerization. Polymer 2012, 53, 5242−5250. (17) Rwei, S. P.; Tseng, Y. C.; Chiu, K. C.; Chang, S. M.; Chen, Y. M. The Crystallization Kinetics of Nylon 6/6T and Nylon 66/6T Copolymers. Thermochim. Acta 2013, 555, 37−45. (18) Mo̷ ller, C.; Plesset, M. S. Note on an Approximation Treatment for Many-Electron Systems. Phys. Rev. 1934, 46, 618−622. (19) Sun, H.; Lee, H. H.; Blakey, I.; Dargaville, B.; Chirila, T. V.; Whittaker, A. K.; Smith, S. C. Multiple Hydrogen-Bonded Complexes Based on 2-Ureido-4 1H -Pyrimidinone: A Theoretical Study. J. Phys. Chem. B 2011, 115, 11053−11062. (20) Dong, H.; Hua, W. J.; Li, S. H. Estimation on the Individual Hydrogen-Bond Strength in Molecules with Multiple Hydrogen Bonds. J. Phys. Chem. A 2007, 111, 2941−2945. (21) Xu, W.; Li, X. C.; Tan, H. W.; Chen, G. J. Theoretical Study on Stabilities of Multiple Hydrogen Bonded Dimers. Phys. Chem. Chem. Phys. 2006, 8, 4427−4433. (22) Su, M. D.; Chu, S. Y. Density Functional Study of Some Germylene Insertion Reactions. J. Am. Chem. Soc. 1999, 121, 4229− 4237. (23) Iche Tarrat, N.; Barthelat, J. C.; Vigroux, A. Theoretical Study of Specific Hydrogen-Bonding Effects on the Bridging P-OR Bond Strength of Phosphate Monoester Dianions. J. Phys. Chem. B 2008, 112, 3217−3221. (24) Gomez, P. C.; Galvez, O.; Escribano, R. Theoretical Study of Atmospheric Clusters: HNO3-HCl-H2O. Phys. Chem. Chem. Phys. 2009, 11, 9710−9719. (25) Sun, T.; Wang, Y. B. Calculation of the Binding Energies of Different Types of Hydrogen Bonds Using GGA Density Functional and Its Long-Range, Empirical Dispersion Correction Methods. Acta Phys-Chim. Sin. 2011, 27, 2553−2558. (26) Bryantsev, V. S.; Diallo, M. S.; van Duin, A. C. T.; Goddard, W. A. Evaluation of B3LYP, X3LYP, and M06-Class Density Functionals for Predicting the Binding Energies of Neutral, Protonated, and Deprotonated Water Clusters. J. Chem. Theory Comput. 2009, 5, 1016−1026. (27) Xantheas, S. S. On the Importance of the Fragment Relaxation Energy Terms in the Estimation of the Basis Set Superposition Error Correction to the Intermolecular Interaction Energy. J. Chem. Phys. 1996, 104, 8821−8824. (28) Valiron, P.; Mayer, I. Hierarchy of Counterpoise Corrections for N-Body Clusters: Generalization of the Boys-Bernardi Scheme. Chem. Phys. Lett. 1997, 275, 46−55. (29) Boys, S. F.; Bernardi, F. Calculation of Small Molecular Interactions by Differences of Separate Total Energies - Some Procedures with Reduced Errors. Mol. Phys. 1970, 19, 553−566. (30) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.; Petersson, G. A.; Nakatsuji, H.; Caricato, M.; Li, X.; Hratchian, H. P.; Izmaylov, A. F.; Bloino, J.; Zheng, G.; Sonnenberg, J. L.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.;

Montgomery, J. A., Jr.; Peralta, P. E.; Ogliaro, F.; Bearpark, M.; Heyd, J. J.; Brothers, E.; Kudin, K. N.; Staroverov, V. N.; Kobayashi, R.; Normand, J.; Raghavachari, K.; Rendell, A.; Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.; Rega, N.; Millam, N. J.; Klene, M.; Knox, J. E.; Cross, J. B.; Bakken, V.; Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Martin, R. L.; Morokuma, K.; Zakrzewski, V. G.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Dapprich, S.; Daniels, A. D.; Farkas, Ö .; Ortiz, J. V.; Cioslowski, J.; Fox, D. J. Gaussian 09, revision A.02; Gaussian, Inc.: Wallingford, CT, 2009. (31) Solomon, O.; Ciuta, I. Determination of the Intrinsic Viscosity of Polymer Solutions by a Simple Determination of Viscosity. J. Appl. Polym. Sci. 1962, 6, 683−686. (32) Porfyris, A. D.; Papaspyrides, C. D.; Rulkens, R.; Grolman, E. Direct Solid State Polycondensation of Tetra- and Hexa-Methylenediammonium Terephthalate: Scaling up from the TGA MicroReactor to a Laboratory Autoclave. J. Appl. Polym. Sci. 2017, 134, 45080. (33) Papaspyrides, C. D.; Porfyris, A. D.; Vouyiouka, S.; Rulkens, R.; Grolman, E.; Poel, G. V. Solid State Polymerization in a MicroReactor: The Case of Poly(Tetramethylene Terephthalamide). J. Appl. Polym. Sci. 2016, 133, n/a. (34) Al-Sabagh, A. M.; Yehia, F. Z.; Eshaq, G.; ElMetwally, A. E. Ionic Liquid-Coordinated Ferrous Acetate Complex Immobilized on Bentonite as a Novel Separable Catalyst for PET Glycolysis. Ind. Eng. Chem. Res. 2015, 54, 12474−12481. (35) Lan, X. Q.; Zhai, W. T.; Zheng, W. G. Critical Effects of Polyethylene Addition on the Autoclave Foaming Behavior of Polypropylene and the Melting Behavior of Polypropylene Foams Blown with n-Pentane and CO2. Ind. Eng. Chem. Res. 2013, 52, 5655−5665. (36) Li, Y. J.; Zhu, X. Y.; Tian, G. H.; Yan, D. Y.; Zhou, E. L. Multiple Melting Endotherms in Melt-Crystallized Nylon 10,12. Polym. Int. 2001, 50, 677−682. (37) Adriaensens, P.; Pollaris, A.; Carleer, R.; Vanderzande, D.; Gelan, J.; Litvinov, V. M.; Tijssen, J. Quantitative Magnetic Resonance Imaging Study of Water Uptake by Polyamide 4,6. Polymer 2001, 42, 7943−7952. (38) Li, W. H.; Yan, D. Y. Synthesis and Characterization of Nylons Based on Hexadecane Diacid. J. Appl. Polym. Sci. 2003, 88, 2462− 2467. (39) Huang, Y.; Li, W. H.; Yan, D. Y. Preparation and Characterization of a Series of Polyamides with Long Alkylene Segments: Nylons 12 20, 10 20, 8 20, 6 20, 4 20 and 2 20. Polym. Bull. 2002, 49, 111−118. (40) Wang, W. Z.; Wang, X. W.; Li, R. X.; Liu, B. Y.; Wang, E. G.; Zhang, Y. H. Environment-Friendly Synthesis of Long Chain Semiaromatic Polyamides with High Heat Resistance. J. Appl. Polym. Sci. 2009, 114, 2036−2042. (41) García, J. M.; García, F. C.; Serna, F.; de la Peña, J. L. HighPerformance Aromatic Polyamides. Prog. Polym. Sci. 2010, 35, 623− 686. (42) Papaspyrides, C. D.; Porfyris, A. D.; Rulkens, R.; Grolman, E.; Kolkman, A. J. The Effect of Diamine Length on the Direct Solid State Polycondensation of Semi-Aromatic Nylon Salts. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 2493−2506. (43) Zhang, G.; Zhou, Y. X.; Kong, Y.; Li, Z. M.; Long, S. R.; Yang, J. Semiaromatic Polyamides Containing Ether and Different Numbers of Methylene (2−10) Units: Synthesis and Properties. RSC Adv. 2014, 4, 63006−63015. (44) Eersels, K. L. L.; Groeninckx, G.; Koch, M. H. J.; Reynaers, H. Influence of Transreaction Processes on the Morphology of Semicrystalline Aliphatic/Aromatic Polyamide Blends. Polymer 1998, 39, 3893−3900. (45) Eersels, K. L. L.; Groeninckx, G. Influence of Interchange Reactions on the Crystallization and Melting Behaviour of Polyamide Blends as Affected by the Processing Conditions. Polymer 1996, 37, 983−989. 7225


Article

Industrial & Engineering Chemistry Research (46) Brisson, J.; Cote, P. Factors Affecting the Miscibility of Nylon6I/Nylon-6,6. Macromolecules 1996, 29, 1839−1841. (47) Wang, L. L.; Dong, X.; Gao, Y. Y.; Huang, M. M.; Han, C. C.; Zhu, S. N.; Wang, D. J. Transamidation Determination and Mechanism of Long Chain-Based Aliphatic Polyamide Alloys with Excellent Interface Miscibility. Polymer 2015, 59, 16−25. (48) Li, Y. J.; Yan, D. Y.; Zhang, G. S. Crystalline Structure and Thermal Behavior of Nylon-10,14. J. Polym. Sci., Part B: Polym. Phys. 2003, 41, 1422−1427. (49) Li, W. H.; Zhang, G. S.; Huang, Y.; Yan, D. Y.; Wang, J. K.; Zhou, E. Different Crystalline Transition Behavior in Polyamides 12 16, 10 16 and 8 16. Polym. Bull. 2003, 49, 387−394. (50) Cui, X. W.; Yan, D. Y. Synthesis and Characterization of Novel Odd-Even Nylons Based on Eicosanedioic Acid. J. Appl. Polym. Sci. 2004, 93, 2066−2071. (51) Cui, X. W.; Li, W. H.; Yan, D. Y. Investigation on Odd-Odd Nylons Based on Undecanedioic Acid: 1. Synthesis and Characterization. Polym. Int. 2004, 53, 1729−1734. (52) Fornes, T. D.; Paul, D. R. Structure and Properties of Nanocomposites Based on Nylon-11 and −12 Compared with Those Based on Nylon-6. Macromolecules 2004, 37, 7698−7709.

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Effect of Aliphatic Diacid Chain Length on Properties of Semiaromatic

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