Preparation and characterization of polyamide‐6 with three‐branched chains

With trimesinic acid as a molecular weight regulator, the hydrolytic polymerization of ?‐caprolactam was carried out, and nylon‐6 or polyamide‐6 with three‐branched chains was obtained. Through a systematic study of the effects of conditions such as the reaction time and concentration of trimesinic acid on the polymerization, we found that the conversion of caprolactam was almost insensitive to the initial concentrations of the regulators, but the relative viscosity of the polymer decreased with increasing trimesinic acid. Characterization investigations showed that differential scanning calorimetry curves changed from a single peak for normal nylon‐6 to one main peak and one shoulder or one small peak for the branched polymer; the melting point of the star‐shaped nylon‐6 decreased with an increasing amount of trimesinic acid, whereas its crystallization temperature was higher than that of linear‐chain nylon‐6. A wide‐angle X‐ray diffraction study indicated that the crystal structure of the star‐shaped nylon‐6 still belonged to the α form, and the crystallizability of the branched polymer with an elevated amount of trimesinic acid during polymerization did not seem to be weakened; the characteristic absorption of infrared spectra provided indirect evidence for the existence of branched chains in the polymer. Moreover, the mechanical properties of star‐shaped nylon‐6 and linear‐chain nylon‐6 were compared. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3184–3193, 2001     

Reversible plasticization of nylons 6 and 11 with anhydrous ammonia and their deformation by solid-state coextrusion

Reversible plasticization of nylons with anhydrous ammonia is a new concept. In the present studies, nylons 6 and 11 have been plasticized with anhydrous ammonia and subsequently were solid-state coextruded below the melting point. The plasticization is attained by a temporary disruption of the strong hydrogen bonding between amide groups of adjacent nylon chains. Thermogravimetric and infrared analysis show that for the nylons 6 and 11 the amount of ammonia absorbed is 18% and 10% of the weight of the dry samples, respectively. The ammonia incorporation to preformed nylon ribbons prior to extrusion alleviated significantly the processing difficulties encountered with untreated nylons and aided the rapid extrusion of highly oriented states (EDR 12). The extent of orientation is documented by the high total birefringence values (8.25 × 10^?2 for nylon 6 and 5.8 × 10^?2 for nylon 11), by the significant increase in crystallinity (23.5%–53% for nylon 6 and 25.7%–40% for nylon 11), and by the enhanced tensile moduli (13 GPa for nylon 6 and 4 GPa for nylon 11).     

Preparation and characterization of a series of polyamides with long alkylene segments: Nylons 12 20, 10 20,s 20,6 20, 4 20 and 2 20

Summary A series of nylons with long alkylene segments between amide groups were newly prepared by step-heating melt-polycondensation of 1,lS-octadecanedicarboxylic acid with various diamines. The prepared polyamides were characterized carefully. The results show that many properties of the prepared nylons change regularly with the length of methylene segments in diamines. In addition, nylon 2 20 has a relatively low molecular weight and much different melting and thermal decomposition behaviors in comparison with other nylons. Received: 21 June 2OO2/Revised version: 18 September 2002/ Accepted: 18 September 2002 Correspondence to Deyue Yan E-mail: dyyan@mail.sjtu.edu.cn Tel: 0086-21-54742863 Fax: 0086-21-54741297     

Investigation on odd‐odd nylons based on undecanedioic acid: 1. Synthesis and characterization

A series of odd‐odd polyamides were prepared through step‐heating melt‐polycondensation of undecanedioic acid with various diamines. The synthesized nylons were characterized comprehensively by means of elemental analysis, fourier‐transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR), Raman spectra, intrinsic viscosity, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The intrinsic viscosities of the prepared polyamides except nylon 3 11 are 0.70 to 0.87 dl g^?1. The melting temperatures of the odd‐odd nylons range from 182 to 209 °C. In addition, the thermal mechanical properties of nylons 5 11, 7 11, 9 11 and 11 11 were analyzed using dynamic mechanical analysis (DMA). Nylon 3 11 could not undergo DMA due to its low molecular weight. The glass transition temperatures obtained from DMA are in the range 22–39 °C. Copyright © 2004 Society of Chemical Industry     

Copolyamides derived from brassylic acid

Polyamides were prepared from C₆ to C₁₂ diamines with brassylic acid, a linear C₁₃ dicarboxylic acid, derived from Crambe seed oil. One distinct characteristic of these polymers is their low moisture adsorption as compared to nylon 66 and nylon 6. To modify the properties of these nylons, multi-component copolyamides were prepared from hexamethylene diamine and mixtures of brassylic acid with adipic, terephthalic, or isophthalic acids. It was found that the melting points of the co-polyamides were changed by the choice and the levels of the diacids used. The melting point-composition curves all show a eutectic minimum. The glass transition temperature of nylon 6,13 is also changed by the incorporation of other diacids. Water adsorption of nylon 6,13 increases with increased substitution of brassylic acid by other diacids in the order of adipic > isophthalic ≥ terephthalic. Mechanical properties of some copolyamides are in the same range as the commercial nylon 11 and nylon 12. The low moisture absorption, reduced fabrication temperature, and the wide range of properties obtainable through copolymerization make copolyamides derived from brassylic acid potentially suitable as specialty tubing, powder coatings, and molded machine parts. They will be commercially viable when brassylic acid becomes available on a large scale and is competitively priced.     

Synthesis and characterization of novel odd–even nylons based on eicosanedioic acid

A series of novel odd–even nylons based on eicosanedioic acid, including nylons 11/20, 9/20, 7/20, 5/20, and 3/20, were prepared through step‐heating melting polycondensation with various diamines, and the products were comprehensively characterized. The results of FTIR, Raman spectra, NMR, and elemental analysis confirmed that the synthesized polyamides had the expected chemical structures. The viscosity‐average molecular weights of the obtained polyamides were in the range of 6.0 × 10³–1.4 × 10⁴. The melting points of the nylons, determined by differential scanning calorimetry, changed from 167 to 194°C. Thermogravimetric analysis gave the decomposition temperatures of the obtained nylons at about 460°C, except for nylon 3/20. Furthermore, dynamic mechanical analysis (DMA) was applied to nylons 11/20, 9/20, 7/20, and 5/20. The glass‐transition temperatures, measured by DMA, ranged from 29 to 52°C. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2066–2071, 2004     

Processing and properties of poly(p-phenylene benzobisthiazole)/nylon fibers

Composite fibers of poly(p-phenylene benzobisthiazole) (PBT) with nylons were spun from dilute acid solutions. The effects of wet-stretching, heat treatment time, tension, and temperature on the tensile properties are reported. Nylon 6,6 and nylon 6 at several molecular weights were studied. Moduli of 40 GPa and tensile strengths of 375 MPa were achieved for 30/70 PBT/nylon composites. Heat treatment of the nylon/PBT fibers at 160–225°C for 12–19 h increased the tensile modulus by 20–50% and the tensile strength by a smaller amount. At the same time, the intrinsic viscosity of the nylons increased as much as 100%, indicating the solid-state polymerization of the nylon. The largest tensile modulus attained is less than half the theoretical value predicted by a linear “rule of mixtures” as might be expected for an oriented molecular composite. Although differential scanning calorimetry shows a melting transition at temperatures 5–10°C higher than the pure nylons, the composite does not flow at temperatures above this transition. Sulfuric acid dissolves most of the nylon, but does not destroy the mechanical integrity of the fibers; differential scanning calorimetry indicates that the remaining fiber contains little or no nylon. The results are consistent with a microstructure consisting of a microfibrillar network of PBT, surrounded by a separate nylon phase.     

三臂星形端羟基聚丁二烯的阴离子合成及其表征

以叔丁基二甲基硅氧基丙基锂为引发剂,环己烷为溶剂进行阴离子聚合合成三臂星形端羟基聚丁二烯。采用凝胶渗透色谱(GPC)和1H-NMR方法表征了聚合物相对分子质量及其分布、支化度、平均官能度和主链微观结构。研究结果表明,三臂星形端羟基聚丁二烯的相对分子质量分布指数≤1.1,平均官能度和支化度均接近3。     

Living polymerization of methyl methacrylate by novel samarium-based trifunctional initiator

Summary A novel trifunctional samarium enolate, prepared in situ by the reduction of 1,3,5-tris(2-bromoisobutyroyloxymethyl)benzene with SmI₂, has proven to initiate the polymerization of methyl methacrylate (MMA). Characterization of the polymer by ¹H NMR and GPC clearly supported the formation of a star-shaped tri-armed poly(MMA). The resulting star-shaped poly(MMA) possessed narrow molecular weight distribution, and its molecular weight agreed well with the theoretical value, which reveals the quantitative initiation efficiency. Received: 6 July 2000/Revised version: 25 August 2000/Accepted: 29 August 2000     

Thermal decomposition of aliphatic nylons

An overview of the literature together with selected authors' data on thermal and thermo-oxidative decomposition of commercial aliphatic nylons (nylon 6, nylon 7, nylon 11, nylon 12, nylon 6.6, nylon 6.10, nylon 6.12) is presented. Despite the high level of research activity and the large number of publications in the field, there is no generally accepted mechanism for the thermal decomposition of aliphatic nylons. Polylactams (nylon 6, nylon 11 and nylon 12) tend to re-equilibrate to monomeric or oligomeric cyclic products. Diacid–diamine type nylons (nylon 6.6, nylon 6.10 and nylon 6.12) produce mostly linear or cyclic oligomeric fragments and monomeric units. Because of the tendency of adipic acid to fragment with elimination of CO and H₂O and to undergo cyclization, significant amounts of secondary products from nylon 6.6 are reported in some papers. Many authors have shown that the primary polyamide chain scission occurs either at the peptide C(O) NH or at adjacent bonds, most probably at the alkyl–amide NH CH₂ bond which is relatively the weakest in the aliphatic chain. Hydrolysis, homolytic scission, intramolecular C H transfer and cis-elimination (a particular case of C H transfer) are all suggested as possible primary chain-scission mechanisms. There are no convincing results reported which tend to generally support one of these mechanisms relative to the others; rather, it seems that the contribution of each mechanism depends on experimental conditions. This conclusion is also supported by the wide spread of kinetic parameters measured under the different experimental conditions. More uniform results are observed in the literature regarding the mechanism of thermo-oxidative decomposition of aliphatic nylons. Most authors agree that oxygen first attacks the N-vicinal methylene group, which is followed by the scission of alkyl–amide N C or vicinal C C bond. Alternatively, it is suggested that any methylene group which is β-positioned to the amide group methylene can be initially oxidized. There are few mechanisms in the literature which explain discoloration (yellowing) of nylons. UV/visible active chromophores are attributed either to pyrrole type structures, to conjugated acylamides or to conjugated azomethines. Some secondary reactions occurring during the thermal or thermo-oxidative decomposition lead to crosslinking of nylons. Nylon 6.6 crosslinks relatively easily, especially in the presence of air, whereas nylon 11 and nylon 12 crosslink very little. Strong mineral acids, strong bases, and some oxides or salts of transition metals catalyse the thermal decomposition of nylons, but minimize crosslinking. In contrast, many fire retardant additives promote secondary reactions, crosslinking and charring of aliphatic nylons. © 1999 Society of Chemical Industry     

Study on a novel N-functionalized multilithium initiator and its application for preparing star-shaped N-functionalized styrene-butadiene rubber

A novel N-functionalized multilithium (N-M-Li) initiator was synthesized from divinylbenzene (DVB) and lithiohexamethyleneimine (LHMI), and its microstructure and molecular weight distribution were characterized by ¹H-NMR and GPC, respectively. Reaction kinetics of synthesis of N-M-Li was also studied and the apparent propagation rate constants of different monomers in this reaction were obtained. Star-shaped N-functionalized styrene-butadiene rubber (SBR) was prepared by anionic polymerization using N-M-Li as initiator, N,N,N′,N′-tetramethylethylenediamine (TMEDA) as polar additive, and cyclohexane as solvent. The molecular weight distribution of the target product was measured by GPC and the result showed that it contained a certain amount of star-shaped polymers. Three types of SBR were initiated by N-M-Li, LHMI, and n-BuLi, respectively, and then were contrasted in terms of the loss factor (tan δ) by DMA, which demonstrated that N-M-Li initiator could provide rubbers with improved hysteresis characteristics. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Amine-terminated nylon 6/66/1010 (AM-6/66/1010) used for hot melt adhesives: synthesis and properties

A new amine-terminated nylon 6/66/1010 (AM-6/66/1010) copolyamide hot melt adhesive with the molecular weight of 21,000–96,000 Da was synthesized and blocked with 1-hexadecylamine. The AM-6/66/1010 samples were characterized by ¹H-NMR spectroscopy, differential scanning calorimetry (DSC), thermal gravimetric analysis, and gel permeation chromatography. The ¹H-NMR spectroscopy demonstrated that 1-hexadecylamine functions as blocking agent in this polymerization. The DSC thermograms showed that the extra peak (peak (II)) and the melting peak (peak (I)) of AM-6/66/1010 are moving left and the glass transition temperature of AM-6/66/1010 decreases as the mole ratio α_H/C (1-hexadecylamine/total carboxyl) increases. The thermal gravimetric analysis indicated that AM-6/66/1010 hot melt adhesive has a high thermal stability. The peel strength of the test specimen obtained by hot melt glutinous lining of AM-6/66/1010 or AC-6/66/1010 and fabric 6535 (65% PET, 35% cotton) was studied using T-peel tests, and the results showed that the washable and dry-cleaning resistant of AM-6/66/1010 copolyamide hot melt adhesive is better than that of carboxyl-terminated nylon 6/66/1010 (AC-6/66/1010) copolyamide hot melt adhesive.     

Preparation of conductive nylon 6 film

Electrically conducting nylon 6 films was prepared by introducing amide group or cyan group into the nylon 6 film and then introducing Cu_xS, which is known as the p-type semiconductor, into the grafted nylon films. The graft copolymerization of acrylamide (AM) and acrylonitrile (AN) onto nylon 6 film was investigated using ceric salt as the initiator. The graft yield was influenced by the concentration of ceric salt, sulfuric acid and monomer, and the reaction time. The optimum conditions for the introducing of Cu_xS were studied. Electrical conductivity of Cu_xS-treated nylon film was found to be higher by order of 10⁹ than that of the original nylon 6 film, and then properties of the resulting modified films were investigated.     

The Structural Causes of the Dyeing Variations of Nylon Yarns Subjected to Dry Heat

When nylon 6 and nylon 6.6 yarns are subjected to dry heat in a texturing machine, the subsequent rate of dyeing with Durazol Blue 2R at first falls and then increases with increasing temperature of heat treatment. It becomes greater than that of the unheated yarn for samples that have been preheated to temperatures near the melting point of the nylons. It has been shown that Fick's law is valid for nylon 6.6 dyed with Durazol Blue 2R in an infinite dyebath. This does not hold for nylon 6, so that, in consequence, for characterising the dyeing process for both nylons the rate of dyeing is a better parameter than the diffusion coefficient. Measurements of density, birefringence, and degree of lateral order by an X-ray method show that these are all increased by the heat treatments. The moisture regain is, however, decreased, but little change is produced in the amine end-group content and X-ray orientation in the samples. An explanation of the dyeing results in relation to the physical and chemical changes is advanced. A morphological structure is envisaged of long ribbon-like units held together by binding material that allows an increase in the relative size of voids, or the total void content, on heating the nylons above a certain temperature, this temperature depending on the particular nylon.     

Preparation and properties of hydrophobic MMA floor coatings based on fluorine-containing methacrylic ester copolymers

In this article, fluorine-containing methacrylic ester copolymers were successfully synthesized by a two-stage suspension polymerization and applied in manufacturing hydrophobic methyl methacrylate (MMA) floor coatings. The copolymer composition was characterized by Fourier transform infrared spectroscopy and proton nuclear magnetic resonance (¹H-NMR) spectroscopy. In addition, the mass fractions of 2-(perfluoroalkyl)ethyl methacrylate (FMA) incorporated in the copolymers were calculated according to the relative intensity of characteristic peaks in the ¹H-NMR spectrum. The prepared hydrophobic MMA floor coatings were analyzed for their coating properties such as viscosity, pot life, dry time, hardness, abrasion resistance, impact resistance, tensile strength, chemical resistance, and contact angle. Accordingly, the influence of the copolymer molecular weight and that of the incorporated amount of FMA in the copolymers were studied. Results show that coatings prepared using the copolymers with a molecular weight of 52,000 exhibit excellent comprehensive properties. Moreover, the contact angle of the coating films prepared increases as the incorporated amount of FMA increases, reaching the maximum value of 103° for 13%.     

Synthesis and characterization of nylons based on hexadecane diacid

A series of nylons with long alkane segments between amide groups were synthesized by using hexadecane diacid and various diamines, and the resulting polyamides were characterized comprehensively. It was shown that the molecular weights of nylons 6 16, 8 16, 10 16, and 12 16 in our studies exceed 1.1 × 10⁴, whereas nylons 2 16 and 4 16 have relatively low molecular weights. In addition, the melting temperatures, the decomposition temperatures, and the glass transition temperatures of the nylons obtained were measured. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2462–2467, 2003     

Ferroelectric switching in spin-coated nylons 11 and 12

Here, we investigate the correlation between the crystal structures and the ferroelectric switching by a sinusoidal alternative electric field for spin-coated nylon 11 films as an odd nylon and for nylon 12 as an even nylon. These spin-coated nylons afforded thin films with thicknesses ranging from 101 to 125 nm. The obtained thin films were subjected to melt-quenching, melt-cooling down, annealing-quenching, or annealing-cooling down. These processes were notably related to the resulting crystal structures. In particular, the crystal structures involving twisted bonds in the molecular chains were significantly related to ferroelectricity in both nylon 11 and nylon 12. Namely, the vector component of the amide dipole moments is transverse to the direction of the molecular chains, which is induced by the presence of more twisted bonds and is significantly related to the remanent polarization P_r for both nylons. In nylon 11, the hydrogen bonding interaction between the intermolecular amide dipole moments in the α and δ crystal forms was weakened by the existence of more twisted bonds. In nylon 12, the nonpolar γ crystal form was transformed to a polarizable γ’ crystal form because of the existence of more twisted bonds. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48438.     

Synthesis of biodegradable pentaarmed star-block copolymers via an asymmetric BIS-TRIS core by combination of ROP and RAFT: From star architectures to double responsive micelles

Biodegradable star-shaped poly(?-caprolactone) and poly(?-caprolactone-b-l-lactide) (5sPCL-b-PLLA) with five arms were synthesized by ring-opening polymerization (ROP) from an asymmetric BIS-TRIS core via “core-first” strategy. Subsequently, a series of amphiphilic and double responsive star-block copolymers were synthesized by Z-RAFT star polymerization of N,N-dimethylamino-2-ethyl methacrylate (DMAEMA) from the star-shaped macro-RAFT agent, which was prepared by attaching 3-benzylsulfanylthiocarbonylthiocarbonylsufanylpropionic acid (BSPA) to 5sPCL-b-PLLA using a simple two-step reaction sequence. GPC and ¹H NMR data demonstrated the polymerization courses are under control. The molecular weight of 5sPCL-b-PLLA-b-DMAEMA increased with the monomer conversion, and the molecular weight distribution was in the range of 1.19-1.37. The spherical micelles with degradable core and pH/thermo-double sensitive shell had been prepared from the aqueous medium of the amphiphilic star-shaped copolymers by dialysis method. Both pH and thermal-responsive behaviours of copolymer micelles obtained in this study were investigated. The micelle size and morphology were measured by DLS, AFM and TEM.     

Effect of nanoclay on the thermal,mechanical, and crystallization behavior of nanofiber webs of nylon‐6

Nylon‐6 and nanoclay/nylon‐6 composite nanofibers were prepared by electrospinning technique, in which formic acid was used as a solvent for good solubility of nylon‐6. The diameter of nylon‐6 and nanoclay/nylon‐6 nanofibers was below 350 nm and had smooth surfaces. The DSC heating curves of nylon‐6 and composites nanofibers show two endotherm behaviors, T_m1 (about 214°C) and T_m2 (about 220°C), corresponding to the melting events of γ‐form and α‐form crystals, respectively. The WAXs study showed that the γ‐crystalline phase predominantly present in both nylon‐6 and nanoclay/nylon‐6 nanofibers. The mechanical properties of the nanoclay/nylon‐6 composite nanofibers were higher than neat nylon‐6 electrospun nanofibers, which was decreased as the quantity of the clay increased. It might be due to the aggregation of nanoclay at high concentration. The thermal properties of the composite nanofibers were higher than neat nylon‐6 nanofibers. POLYM. COMPOS., 2012. © 2011 Society of Plastics Engineers     

Synthesis of mid-dicarboxy polystyrene by ATRP and formation of ionic-bonded supramolecules

Dimethyl 4,6-bis(bromomethyl) isophthalate was synthesized by bromomethylation, oxidation, esterification and bromination of 1,3-dimethylbenzene. This was used to initiate the atom transfer radical polymerization of styrene successfully. Results showed that the process had some of the good characteristics of controlled/living free radical polymerization. The molecular weight of the obtained polymer increased linearly with monomer conversion, its molecular weight distribution was very narrow, and a linear relationship between ln([M]₀/[M]) and polymerization time was found. A well-defined novel structural polystyrene containing two ester groups in the mid-main chain was prepared with controlled molecular weight and narrow polydispersity. The structure of the polymer was confirmed by ¹H-NMR spectra. After being hydrolyzed, dicarboxy polystyrene was obtained and used to form ionic-bonded supramolecules with 1-dodecanamine as a model of the star-shaped supramolecules. The supramolecules formed were characterized by Fourier transform infrared (FTIR) spectrum. Translated from Acta Polymerica Sinica, 2006, (4): 597–602 [译自: 高分子学报]