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Difunctional glycidyl azide polymer (GAP) is an energetic binder promising for propellant formulations. The multifunctional fluorine‐containing GAP has been synthesized to enhance its mechanical properties. This work outlined multifunctional GAP partially grafted with 1,2,3‐triazole‐5‐(α‐hydroxyl)‐fluorinated polyether (GAP‐g‐3F) synthesized by thermal and catalyst‐free azide‐alkyne cycloaddition reaction, in which the azide groups were from GAP and electron‐deficient alkynes from β‐propargyl‐α‐hydroxyl poly (tri‐fluoropropane glycidyl ether) (PHP3F). PHP3F was synthesized via the typical cationic ring‐opening polymerization of 2‐((2,2,2‐trifluoroethoxy) methyl) oxirane and propargyl alcohol as the initiator. The chemical structures, molecular weight, and thermal properties were characterized by FTIR, NMR, GPC, DSC, and TGA, respectively. HNMR results showed that 8 % of total azide groups in GAP were grafted. GAP‐g‐3F had a slightly higher glass transition temperature than that of GAP. The results of TGA showed that GAP‐g‐3F had suitable thermal decomposition resistance up to 200 °C. The thermal properties, mechanical properties, cross‐linking network structures, and microstructures of the polyurethane networks cured with hexamethylene diisocyanate trimer as a crosslinking agent were determined and compared by TGA, universal tensile test, swelling measurement, and SEM, respectively. The initial decomposition temperature of GAP‐g‐3F‐based polyurethane networks (GAP‐g‐3F‐PU) was around 220 °C, thus meeting the requirements for propellants. In addition, GAP‐g‐3F‐PU exhibited superior mechanical properties, showing an almost twelvefold increase in tensile strength to 16.9 MPa compared with difunctional GAP‐PU with 1.4 MPa tensile strength. The results of the swelling measurement revealed that the GAP‐g‐3F‐PU sample showed a higher crosslinking density in comparison to the GAP‐PU sample. SEM results indicated that the multifunctional fluorine‐containing GAP could enhance compatibility between the soft and hard segments of polyurethanes, leading to a decrease in their separation degree. This finding showed that the synthesis of a multifunctional GAP partially grafted with fluorinated polyether via a triazole ring may be a promising solution to decrease the separation degree increase of PUs, thereby improving the mechanical properties. [ABSTRACT FROM AUTHOR]

This work reports the kinetics of anionic ring‐opening polymerization of hexaethylcyclotrisiloxane (D3Et) with potassium trimethylsilanolate as initiator and diglyme and N,N‐dimethylformamide (DMF) as promoters. The polymerization rate of D3Et is influenced by the nature of promoters and the reaction temperatures. With the use of DMF as a promoter, the polymerization activation energy is 107.89 kJ/mol, and the polymerization rate constant at 110°C is 0.08466 min−1 with [P]/[I] = 3.0. Gel permeation chromatography and 29Si NMR spectra showed that the intermolecular redistribution occurred during the late stage of polymerization, which facilitated the synthesis of high‐molecular‐weight polydiethylsiloxane (PDES). Differential scanning calorimetry analysis showed that PDES exhibited a glass transition temperature of −142°C and complex crystallization phenomena. Thermogravimetric analysis illustrated that the PDES that was prepared using this method had good thermal stability with onset decomposition temperatures of 483 and 452°C under nitrogen and air conditions, respectively. This work presents innovative approaches for achieving a more energy‐efficient synthesis of PDES to meet the demands of industrial‐scale production. [ABSTRACT FROM AUTHOR]

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Photocurable polymer provides fast curable properties via ultraviolet (UV) light for 3D‐printed propellants. This work outlines the preparation and characterization of photocurable fluorinated polyether‐based reactive inks. Acrylate‐terminated poly‐2‐((2,2,3,3,3‐pentafluoropropoxy)‐methyl) ethylene oxide (P5F‐AA) was synthesized as photocurable binder through the esterification of acrylic acid, and the terminal hydroxyl group of poly‐2‐((2,2,3,3,3‐pentafluoropropoxy)‐methyl) ethylene oxide (P5F), which was synthesized through cationic ring‐opening polymerization of 2‐((2,2,3,3,3‐pentafluoropropoxy)methyl) oxy‐ethane (PFEE) by using butane diol as initiator. In comparison with P5F, P5F‐AA had a lower glass transition temperature (Tg) of −63.3°C. A new type of photocurable resin, which may be used for additive manufacturing of energetic materials, was prepared via UV radiation in an LED UV curing tank by using P5F‐AA as prepolymer, diphenyl (2,4,6‐trimethyl benzoyl) phosphine oxide (TPO) as photo‐initiator, and tri‐fluoroethyl acrylate (3F‐AA) and 1,6‐hexanediol diacrylate (HDDA) as mono‐ and multifunctional diluents, respectively. When the mass ratio of P5F‐AA/3F‐AA/HDDA binder matrix was 1:1:0.5, the sample exhibited maximal mechanical strength of 6.56 MPa with elongation at break of 13.38%, which was due to the introduction of HDDA effectively increasing the "entanglement" between molecular chains. Thermogravimetric analysis (TGA‐DTG) was utilized to evaluate the ability to decompose thermally of the binder matrix, and the results showed the initial degradation temperature started at nearly 181°C and two consecutive stages in thermal decomposition. Overall, the obtained results from the different techniques suggested that P5F‐AA/3F‐AA/HDDA binder matrix may be a photocurable reactive ink for 3D‐printed propellants, which would provide a certain reference value and guiding importance for design of reactive inks. [ABSTRACT FROM AUTHOR]

This contribution reports the efficient conversion of γ‐valerolactone and its derivatives, abundant but unexplored renewable feedstocks, into sustainable and degradable polythioesters via the establishment of the first isomerization‐driven ring‐opening polymerizations (IROPs) of corresponding thionolactone intermediates. The key to this success relies on the development of a new simple and robust [Et3O]+[B(C6F5)4]− cationic initiator which possesses high activity, exclusive selectivity, living nature, and broad scope of thionolactones. A complete inversion of configuration during IROP of enantiopure γ‐thionovalerolactone is also disclosed, affording isotactic semicrystalline polythioesters (Tm=87.0 °C) with mechanical property compared well to the representative commodity polyolefins. The formation of a highly crystalline supramolecular stereocomplex with enhanced thermal property (Tm=117.6 °C) has also been revealed. [ABSTRACT FROM AUTHOR]

• Synthesis of biobased polyamide 4 by anionic polymerization of 2-pyrrolidone. • Preparation of nanofibers by electrospinning and their characterization. • Test of degradation of nanofibers in water environment for a long period. • Nanofiber layers are hydrolytically stable. Based on renewable raw materials, polyamide 4 has excellent mechanical properties, high hydrophilicity, and cotton-like water sorption. The problem is its low thermal stability near its melting point, which does not allow melt processing. With the development of the technology of electrostatic spinning of polymers from solutions, the attention of researchers has returned to polyamide 4. In this work, nanofiber layers of polyamide 4 with molar masses of 18,000 and 280,000 g/mol and diameters of 350 ± 60 and 270 ± 10 nm, respectively, were prepared by electrostatic spinning from a mixed solution of formic acid and dichloromethane. Subsequently, the layers were subjected to degradation in phosphate buffer at 37 and 60 °C. The electrostatic spinning process was shown to result in a decrease in the molar mass of the samples. During degradation in buffer at pH 7.4, the molar mass does not change significantly, but there is a change in the structure of the nanofibrous layers by bonding of the fibers, especially for low molecular weight PA4. In contrast to other studies, polyamide 4 is hydrolytically stable even in the form of nanofiber layers. [ABSTRACT FROM AUTHOR]

Low dielectric photoinduced patterned materials have attracted extensive attention owing to their potential applications in integrated circuits and semiconductor devices. In this work, we synthesized a low dielectric polymer that can be used for photolithography. The monomer, 1-(4-vinylphenyl)-2-(4-benzocyclobutenyl)ethene (DVB-S-BCB), was synthesized from divinylbenzene (DVB) and 4-bromobenzocyclobutene (4-BrBCB) using the Heck reaction. Subsequently, P-DVB based on DVB-S-BCB was prepared by anionic polymerization. As the structure comprised thermally curable benzocyclobutene (BCB) groups and photocurable vinyl groups (UV/Thermal dual curing structure), P-DVB has been used for high-performance negative photosensitive resin with 2,6-bis(4-azidobenzylidene) cyclohexanone (BAC) as a photoinitiator. Photolithography was carried out using a 365-nm UV light source to obtain various patterns, and the research results indicate that photosensitive resins exhibit stable patterning processes at different curing stages. Besides, the cured P-DVB exhibited high thermal stability (T 5% above 420 °C in N 2), low dielectric constant (2.55 at 10 MHz), low dielectric loss (1.56 × 10−3 at 10 MHz), and excellent mechanical performance. These properties make P-DVB a potential photoresist that can be widely used as interconnected dielectrics. P-DVB containing vinyl groups and benzocyclobutene groups was synthesized by anionic polymerization. This resin exhibits low D k and high-resolution photo-imageable dielectric performance. Therefore, it is expected to be used for integrated circuits and semiconductor devices. [Display omitted] • Rapid synthesis of photosensitive resins with photo-thermal curing structures on a large scale, and at low cost. • Have high-resolution photo-imageable and process flexibility (spin coating or dry film, patterning, developing). • UV/Thermal double cured structure gives excellent mechanical properties, low dielectric properties and low CTE. • Widely used in high-density, low-power packages such as WLP, RDL, TSV, etc., promoting integration and miniaturization. [ABSTRACT FROM AUTHOR]

Copolymerization of diallylamine (DAA) and itaconic acid (IA) was synthesized using benzoyl peroxide as a free radical initiator, in dioxane as the solvent. The composition of the copolymer was determined by the nitrogen content using Edx. The solubility of the copolymer was also investigated. The water solubility of the synthesized copolymer depends on the comonomers' ratio. The structure of the copolymer was confirmed by 13C-NMR spectroscopy. To increase the water insolubility of the copolymers, and keep their hydrophilicity, the copolymer was allowed to react with chitosan to form a superabsorbent polymeric material (SP). The structure of the synthesized superabsorbent was confirmed using 13C-NMR spectroscopy. The thermal property of the (SP) was also investigated by TGA. The investigation of the chitosan-based superabsorbent, as water-retaining agents, was studied. The results revealed that the superabsorbent polymers exhibited a good swelling ability and salt tolerance. [ABSTRACT FROM AUTHOR]

Copyright of Silicone Material is the property of Silicone Material Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The weakly entangled ultrahigh molecular weight polyethylene (UHMWPE) was synthesized by a Ziegler‐Natta catalyst, where the titanium tetrachloride was anchored on the polystyrene (PS)‐modified silica. The PS chains were successfully incorporated into silica hierarchical pores even with the size less than 10 nm through the in situ free‐radical polymerization of styrene. The self‐diffusion coefficient and crystallization of probing molecules inside the pores were investigated by the pulsed field gradient NMR and thermoporosimetry to address the swollen behavior of incorporated PS blocks. This PS blocks compartmentalized the polyethylene chains, where the less entangled UHMWPE was synthesized with an exceptional activity at 70°C. The ubiquitous PS isolators effectively hindered the formation of chains overlaps during the polymerization, showing a long‐term efficiency to reduce the entanglements of nascent UHMWPE even at 4 h of polymerization The toughness/stiffness/strength balance of weakly entangled UHMWPE was significantly improved. [ABSTRACT FROM AUTHOR]

Neat and hybrid polyamide 12 (PA12) based powders are important raw materials for additive manufacturing. This study describes a facile method for the synthesis of pure, hybrid and copolymeric microparticulate materials based on one‐pot activated anionic ring‐opening polymerization (AAROP) of laurolactam in solution. The results reveal the possibility to obtain in good yields, for reaction times of 2 h and temperatures of up to 110°C neat and hybrid PA12 microparticles (MP) carrying metal or carbon fillers. Copolymeric PA12/PA6 MP can also be successfully prepared. All MP materials are analyzed by spectral, microscopy, thermal, and synchrotron X‐ray scattering methods in order to clarify their morphology, chemical and crystalline structure, melting and degradation behavior. The melting temperature of the PA12 MP is lower than of the commercial PA12, the presence of metal particles or copolymerization with PA6 additionally decrease it well below 170°C. The composites prepared by compression molding of PA12 MP display elastic modulus of up to 1.49 GPa, the stresses at yield and break reaching 50 and 69 MPa, respectively. It is concluded that the neat, hybrid, and copolymeric pulverulent materials obtained via microencapsulation by AAROP in solution may be useful in additive manufacturing processing. [ABSTRACT FROM AUTHOR]

UV‐initiated cationic frontal polymerization is exploited as a solvent‐free, extremely fast, and low‐temperature technique to obtain epoxy‐based adhesives. Epoxy formulations are prepared by blending commercial resins at different weight ratios and adding photo and thermal initiators at different percentages. In addition, the influence of other critical parameters, including the joint thickness, the nature of the adherends, and the temperature, is studied. As the reaction front is thermally sustained, the boundary conditions play a key role during the curing process and heat dissipation through the adherends in particular. The thermal properties of the epoxy formulation are studied through differential scanning calorimetry analysis, and the joint strengths are investigated by carrying out single lap off‐set shear tests under compression. The results demonstrate the feasibility of obtaining joints by means of the radical induced cationic frontal polymerization of the epoxy adhesives, which exhibit comparable epoxy group conversion and mechanical performances to the ones cured by traditional energy‐intensive techniques. [ABSTRACT FROM AUTHOR]

Preparing an epoxy resin with biomass resources as an alternative for bisphenol A is significant for sustainable and renewable development under great pressure of limited fossil resources and urgent environmental issues. Herein, we synthesized an epoxy oligomer P-DBP-EP-n derived from biomass magnolol through an efficient one-step glycidylation. P-DBP-EP-n exhibited a low viscosity of 11.7 Pa·s at room temperature, endowing it with excellent processability as diglycidyl ether of bisphenol A (DGEBA) and magnolol-based epoxy monomer EDBP. Then P-DBP-EP-n was cured with a diamine curing agent, 4,4'-diaminodiphenyl methane (DDM), and following thermal addition polymerization of allyl units. Compared with DGEBA/DDM and EDBP/DDM, P-DBP-EP-n/DDM possessed a higher glass transition temperature (Tg) (304 to 167 and 226 °C), implying distinguished heat resistance. Furthermore, the tensile properties and notched impacted strength of P-DBP-EP-n/DDM were better than EDBP/DDM (20.7 to 19.4 MPa, 2.0 to 1.6 GPa, and 2.5 to 2.0 kJ/m²). The initial degradation temperature and char residue of P-DBP-EP-n/DDM were 421 °C and 35.2%, with a 13.5 and 101% increase compared with those of DGEBA/DDM, respectively. Additionally, P-DBP-EP-n/DDM displayed outstanding flame retardancy with V-0 rate for the vertical burning test and limiting oxygen index value of 47.7%, which was almost twice as much as that of DGEBA/DDM. This study offers a promising and feasible pathway to obtain a fully bio-based epoxy resin substituted for petroleum-based DGEBA with distinguished processability, heat resistance, and flame retardancy. Comprehensive properties of the bio-based thermosets are expected to be further regulated by the thermal addition polymerization of allyl units. [ABSTRACT FROM AUTHOR]

In the available research, firstly a new 3-acetamido phenyl acrylate (APhA) monomer and a novel copolymer containing acetamido phenyl group were synthesized. 3-acetamido phenyl acrylate (APhA) monomer was acquired by the reaction of acryloyl chloride and N-(3-hydroxyphenyl) acetamide. 3-acetamido propyl methacrylate (AAPMA) monomer was prepared in our previous study. A series of copolymers were prepared using these monomers in different mole ratios by free-radical polymerization method at 70 °C The structure of P(AAPMA-co-APhA) copolymer systems was characterized by FT-IR and NMR techniques. Thermal characteristics of P(AAPMA-co-APhA) copolymers were evaluated through thermogravimetric analysis (TGA) and differential scanning calorimeter (DSC) in an N2 atmosphere. Due to the presence of the amide group, we can say that the polymer with the least weight loss and the highest residue percentage at 500 °C is poly(APhA). AC electrical conductivity and dielectric and electrical parameters were analyzed in a range of 100 Hz–20 kHz frequency. The dielectric constant values of poly(AAPMA-co-APhA0.63) and P(AAPMA-co-APhA0.30) were 4.98 and 4.57 respectively. According to the results, the dielectric value decreased as the APhA units increased. [ABSTRACT FROM AUTHOR]

Two different Schiff bases, viz. 1-{4-[(5-bromo-2-hydroxybenzyliden)amino]phenyl}ethanone (5-Br-2HBAPE) and 1-{4-[(4-hydroxybenzylidene)amino]phenyl}ethanone (4-HBAPE), have been prepared by condensation of 5-bromosalicylaldehyde and 4-hydroxybenzaldehyde with 4-aminoacetophenone in ethanol at molar ratio of 1:1. Then, Schiff base methacrylate monomers, i.e., 2-(((4-acetylphenyl)imino)methyl)-4-bromophenylmethacrylate (APIMBPM) and 2-(((4-acetylphenyl)imino)methyl)phenylmethacrylate (APIMPM), were synthesized by reaction of each Schiff base compound with methacryloylchloride at 0°C to 5°C. Schiff base methacrylate polymers poly(APIMBPM) and poly(APIMPM) were then prepared by free-radical polymerization in tetrahydrofuran (THF) at 70°C using azobisisobutyronitrile (AIBN) as initiator. The structure of 5-Br-2HBAPE, 4-HBAPE, APIMBPM, APIMPM, poly(APIMBPM), and poly(APIMPM) was confirmed by Fourier-transform infrared (FT-IR) and 1H and 13C nuclear magnetic resonance (NMR) spectroscopy. The thermal behavior of poly(APIMBPM) and poly(APIMPM) was studied by differential scanning calorimetry (DSC) and thermogravimetry (TG). The glass-transition temperature (Tg) of poly(APIMBPM) and poly(APIMPM) was found to be 113°C and 108°C, respectively. The residual amount of poly(APIMBPM) and poly(APIMPM) at 1000°C was found to be 45.60% and 26.35%, respectively. Dielectric and conductivity measurements were carried out on the Schiff base methacrylate polymers by impedance analysis as a function of frequency. The conductivity of poly(APIMBPM) and poly(APIMPM) was found to be 1.30 × 10−9 S cm−1 and 2.14 × 10−9 S cm−1, respectively. Scanning electron microscopy (SEM) was used to investigate the morphology of the Schiff base methacrylate polymers, and their antimicrobial activity against bacteria and fungus was determined by disk diffusion method. Poly(APIMBPM) exhibited good antibacterial property against Klebsiella pneumonia. Poly(APIMBPM) and poly(APIMPM) exhibited good antifungal action against Candida albicans. We thus describe the synthesis of different Schiff base methacrylate polymers and their thermal behavior, electrical properties, and antimicrobial activities. [ABSTRACT FROM AUTHOR]

[Display omitted] An efficient synthesis of the new star-shaped polymer with azido-containing oligomer rays is based on construsion of these rays on the β-cyclodextrin nitrate core employing 3,3-bis(azidomethyl)oxetane as the key reactant. The formation of star-shaped structure was proved. Thermal and optical properties of the synthesized polymers were assessed. [ABSTRACT FROM AUTHOR]

Copyright of Ciencia, Tecnología y Salud is the property of Ciencia, Tecnologia y Salud and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Poly(A)‐block‐poly(B), poly(A)‐block‐poly(B)‐block‐poly(A) and B(A)2 block copolymers were prepared through coordinated anionic ring‐opening polymerization of ε‐caprolactone (CL) and lactic acid (LA) using hydroxy‐terminated polydimethylsiloxane (PDMS) as initiator. A wide range of well‐defined combinations of PDMS‐block‐PCL and PDMS‐block‐PLA diblock copolymers, PCL‐block‐PDMS‐block‐PCL and PLA‐block‐PDMS‐block‐PLA triblock copolymers and star‐PDMS(PCL)2 copolymers were thus obtained. The number‐average molar masses and the structure of the synthesized block copolymers were identified using various analytical techniques. The thermal properties of these copolymers were established using differential scanning calorimetry. Considering PDMS‐block‐PCL copolymers, the results demonstrate the complex effect of polymer architecture and PCL block length on the ability of the PDMS block to crystallize or not. In the case of diblock copolymers, crystallization of PCL blocks originated from stacking of adjacent chains inducing the extension of the PDMS block that can easily crystallize. In the case of star copolymers, the same tendency as in triblock copolymers is observed, showing a limited crystallization of PDMS when the length of the PCL block increases. In the case of PDMS‐block‐PLA copolymers, melting and crystallization transitions of the PLA block are never observed. Considering the diblock copolymers, PDMS sequences have the ability to crystallize. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Model PCL homopolymers (anionic polymerization) were synthetized and chemically functionalized with anhydrides to improve their bio-activity. Modified polyesters were used to fabricate highly porous PCL membranes by leaching technique, reaching porosities values up to 86.1%. Microstructural characterization revealed that chemical modification did not affect thermal properties and mechanical stabilities of PCL membranes. In vitro assays were carried out by soaking samples in simulated body fluid (SBF) solution. By SEM-EDX and TGA analyses, it was observed that modified polyesters exhibited a hydroxyapatite layer over polymeric surfaces, with calcium/phosphorous ratio of 1.58, close to the value reported by literature for hard tissue. [ABSTRACT FROM AUTHOR]

In this study, 2-(bis(cyanomethyl)amino)-2-oxoethyl acrylate (CMA2OEA) monomer, which does not exist in the literature, was synthesized and characterized. Elemental analysis technique, along with classical spectroscopic methods such as FTIR, 1H and 13C NMR, is used in the characterization of the monomer. Further, homopolymer of the CMA2OEA monomer [poly(CMA2OEA)] is synthesized by free radical chain polymerization reaction. Homopolymer synthesized is also characterized by spectroscopic techniques and thermal characterization is investigated by TGA/DTA/DTG thermal analysis methods. [ABSTRACT FROM AUTHOR]

Polystyrene (PS) has low impact strength and also shows poor strain hardening. In this work, poly(styrene–butadiene–styrene) triblock copolymer (SBS) was solution- and melt-blended with PS in the presence of a free-radical polymerization initiator, dicumyl peroxide (DCP), to enhance PS's thermal stability, mechanical properties, impact resistance, and strain hardening. The solution-blended PS/SBS containing 0.1% DCP annealed at 180 °C showed strong strain hardening, but the melt-blended PS/SBS annealed at the same temperature and time showed poor strain hardening. The change in the blending temperature, DCP concentration, and PS-to-SBS ratio had minimal effect on the strain hardening of melt-blended PS/SBS. The tensile strength increased with an increase in the concentration of DCP up to 0.1%, and beyond that level, the tensile strength started decreasing. The impact resistance considerably improved with an increase in the SBS loading in the PS matrix, and the enhancement was more than double of the impact resistance shown by the neat PS. [ABSTRACT FROM AUTHOR]

The elastic constants and vibrational contributions to thermal properties of three polymerizing liquids were investigated by using the available hypersonic velocity measured by Brillouin light scattering in real time. During the addition polymerization to a molecular network structure, Poisson’s ratio υPoisson decreases approximately according to exp[-(ktpolym)]n, where both k and n are composition dependent. The Debye frequency increases and the corresponding heat capacity, energy, and entropy approaching a limiting value. υPoisson of the vitrified polymer continues to decrease but much more slowly, indicating its continued slow polymerization and structural relaxation with time. In the potential energy landscape interpretation, a polymerizing liquid’s state point continuously shifts to another landscape’s more curved, deeper minima. [ABSTRACT FROM AUTHOR]

Oligo(spiroorthocarbonate)s 1, which were synthesized by the polycondensation of pentaerythritol derivatives with tetraethylorthocarbonate, were employed as comonomers in the cationic polymerization of epoxide initiated by sulfonium salt. In the copolymerization, the spiroorthocarbonate moiety of 1 underwent double ring‐opening reaction, leading to the efficient diminution of the volume shrinkage upon the copolymerization. Thermal properties of the resulting networked polymers were evaluated by TGA. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1564–1568 [ABSTRACT FROM AUTHOR]

ABSTRACT: Mushroom polysaccharides (MP), including white MP, brown MP, and enoki MP, were incorporated into cellulose nanofiber (CNF). Studies on thermal property, structure, crystallinity, and morphology of CNF‐MP films revealed that MP was well interacted with and adsorbed onto CNF. Incorporation of MP significantly (P < 0.05) increased tensile strength and reduced water vapor permeability of CNF film. CNF‐MP films possessed higher antioxidant activity than CNF only or CNF‐chitosan film, and the antioxidant activity of released components from CNF‐MP films immersed in water was higher than that released from films immersed in methanol. Radical scavenging activity and reducing ability were major antioxidant mechanisms of CNF‐MP films. These trends were consistent with the results of total phenolics content released from films and the antioxidant activity of MP themselves. This study demonstrated CNF‐MP films may be used as packaging material for preventing oxidation and/or dehydration of food during storage. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46166. [ABSTRACT FROM AUTHOR]

Combination of anionic and ring opening metathesis (ROMP) polymerizations is conducted for the synthesis of different series of brush polymers adopting the macromonomer methodology. Specifically, poly( tert-butoxystyrene) (P tBOS), polystyrene (PS), and poly(ethylene oxide) (PEO) macromonomers, having end norbornene groups, are prepared by anionic polymerization techniques and suitable termination reactions or functional anionic initiators. These macromonomers are either homopolymerized or copolymerized by ROMP employing Ruthenium Grubbs catalysts of the 1st or 3rd generation leading to the formation of polymer brushes. Using this synthetic approach, P tBOS polymacromonomers, P tBOS-PEO block and random copolymacromonomers, and P tBOS-PS random copolymacromonomers are prepared. Acidic hydrolysis of the tert-butoxy groups of the P tBOS brushes affords the corresponding polyhydroxystyrene (PSOH) brushes. Subsequent activation of the hydroxyl groups upon reaction with triphenylmethyl potassium and addition of ethylene oxide lead to the formation of PEO brushes on the PSOH brushes (brush on brush structures). These materials are thoroughly characterized by size exclusion chromatography, and 1H-NMR spectroscopy. The thermal properties are studied by differential scanning calorimetry, thermogravimetric analysis , and differential thermogravimetry. [ABSTRACT FROM AUTHOR]

This experimental and theoretical study deals with the thermal spontaneous polymerization of n-butyl acrylate (n-BA). The polymerization was carried out in solution (n-heptane as the solvent) at 200 and 220 °C without adding any conventional initiators. It was studied with the five different n-BA/n-heptane volume ratios: 50/50, 70/30, 80/20, 90/10, and 100/0. Extensive experimental data presented here show significant monomer conversion at all temperatures and concentrations confirming the occurrence of the thermal self-initiation of the monomer. The order, frequency factor, and activation energy of the thermal self-initiation reaction of n-BA were estimated from n-BA conversion, using a macroscopic mechanistic model. The estimated reaction order agrees well with the order obtained via our quantum chemical calculations. Furthermore, the frequency factor and activation energy estimates agree well with the corresponding values that we already reported for bulk polymerization of n-BA. [ABSTRACT FROM AUTHOR]

ABSTRACT This article investigates the evolution of the thermal conductivity and the coefficient of thermal expansion (CTE) of epoxy composites filled with different silver-plated short glass fibers (Ag@GFs) treated by electroless plating. After electroless plating, the results of X-ray diffraction and scanning electron microscopy showed that glass fibers were coated with pure silver shells whose thickness was controlled via the repetition of electroless plating cycle, and calculated by weighting method. The optical photographs showed that Ag@GFs are randomly oriented and uniformly dispersed in the composites. HotDisk thermal constant analyzer and dilatometer were used to further characterize the thermal conductivity and the CTE of the composites, respectively. The results revealed that the thermal conductivity of Ag@GF/epoxy composites increased with the increase of Ag@GF content, and was adjusted by changing the thickness of silver shell. But the CTE of the composites drops sharply as the Ag@GF content increases compared with neat epoxy. Based on Agari model with fitted factors of Cp and Cf, the calculated thermal conductivity values of Ag@GF/epoxy composites agreed well with the experimental results, and Cp kept almost unchanged, but Cf varied with the change of the thickness of silver shell, despite increasing filler content. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45555. [ABSTRACT FROM AUTHOR]

1,6-hexanediol diacrylate (HDDA) single crystal was grown by slow cooling method. The grown crystal was characterized by single crystal X-ray diffraction, and it showed that HDDA crystallizes in the triclinic system with space group P-1. The cell parameters are a = 6.4885 (9) Å, b = 6.945 (2) Å, c = 7.4890 (12) Å, α = 96.43 (2) °, β = 98.369 (13) °, γ = 109.96 (2) ° and Z = 1. The thermal properties of the HDDA was studied by differential scanning calorimetry (DSC) and showed just one crystalline form existed. A modelization method to judge the possibility of photoinitiating free-radical chain-reaction polymerization in crystal region was established based on the single crystal data, with which the polymerize possibility of HDDA in crystal region was studied. [ABSTRACT FROM AUTHOR]

ABSTRACT Hybrid polymer networks based on unsaturated polyester (UPE) and epoxidized soybean oil acrylate (ESOA) were synthesized by reactive blending through free radical addition polymerization reaction. ESOA was prepared by acrylation of epoxidized soybean oil (ESO). The physical, mechanical, thermal and electrical properties of the cured blends were compared with the neat resin. ESOA resin bearing reactive functional groups showed good miscibility and compatibility with the UPE resin. The co-cured resin showed substantial upgrading in the toughness, impact resistance, thermal properties, and downgrading brittleness up to the addition of 20 wt % of ESOA content. The muddled phase structure was corroborated by Fourier transform infrared spectroscopy, scanning electron microscope, and transmission electron microscopy and proved the formation of excellent hybrid polymer network. An improvement in overall properties has been achieved without seriously affecting any other properties. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44345. [ABSTRACT FROM AUTHOR]

ABSTRACT During the last years, the field of drug delivery has experienced a growing interest toward the so-called thermo-responsive polymers: synthetic materials that, due to the specific hydrophilic-lipophilic balance of their repeating units, exhibit a lower critical solution temperature (LCST) in water associated to a characteristic coil-globule transition. In this work, thermo-responsive amphiphilic block copolymers are synthesized via reversible addition-fragmentation transfer (RAFT) polymerization starting from thermo-responsive monomers and a hydrophobic biodegradable macromonomer, oligo(caprolactone)methacrylate (CL3MA), produced via ring opening polymerization (ROP). The obtained copolymers exhibit an interesting self-assembly behavior leading to nanoparticles (NPs) as long as temperature is kept below the LCST. Otherwise, once this value is overcome, the destabilization of the NPs causes the formation of hydrophobic superstructures that enhance the release of an entrapped lipophilic drug. This characteristic behavior has been systematically studied and related to the copolymer structure. In particular, the self-assembly behavior as well as temperature-triggered NP destabilization have been related to the relative length of the two blocks constituting the copolymers and to their hydrophilic-lipophilic balance (HLB). Finally, the efficacy of the thermo-responsive triggered drug release has been tested in the case of Paclitaxel (PTX). © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 2919-2931 [ABSTRACT FROM AUTHOR]

This study aims at physicochemical properties of thermo- and pH/CO2-responsive cyclic homopolymers. Three examples of cyclic poly(2-(dimethylamino)ethyl methacrylate)s (PDMAs) are synthesized by combining the reversible addition-fragmentation chain transfer process and the Diels-Alder ring-closure reaction. After cyclization, the glass transition temperature significantly increases (Δ Tg = 51.8-59.7 °C) due to the different configurational entropy and end groups, and the maximum decomposition temperature to lose the pendent groups is drastically decreased from 309 to 278 °C. Effects of polymerization degree, polymer concentration, additive of NaCl, and pH/CO2 on lower critical solution temperature behaviors of PDMA aqueous solutions are investigated. The cloud points ( Tc) of ring PDMAs are usually higher than their linear precursors, and the Δ Tc values obtained under a fixed condition can reach up to 20.7 °C, revealing the crucial role of the topology effect. This study paves the way for unique properties and applications of smart cyclic polymers and their derivatives. [ABSTRACT FROM AUTHOR]

A series of poly(polyethylene glycol n -alkyl ether vinyl ether)s (PC m E n VEs) with various lengths of alkyl chains and polyethylene glycol spacers as side chain (m = 16,18; n = 1,2) were synthesized via two steps. First, monomers-ethylene glycol hexadecyl ether vinyl ether (C 16 E 1 VE), ethylene glycol octadecyl ether vinyl ether (C 18 E 1 VE), diethylene glycol hexadecyl ether vinyl ether (C 16 E 2 VE) and diethylene glycol octadecyl ether vinyl ether (C 18 E 2 VE) were synthesized by a modified Williamson etherification. Then, four new types of phase change materials were successfully fabricated by a living cationic polymerization. Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD) were employed to characterize their composition, thermal properties and crystallization behavior. The results show that, the side chains of PC 16 E 1 VE, PC 18 E 1 VE, PC 16 E 2 VE and PC 18 E 2 VE are in a hexagonal lattice, and the onset temperatures for melting of PC 16 E 1 VE, PC 18 E 1 VE, PC 16 E 2 VE and PC 18 E 2 VE are 39.8 °C, 37.4 °C, 51.0 °C and 48.9 °C, the onset temperatures for crystallization are 36.7 °C, 35.2 °C, 47.4 °C and 46.3 °C, respectively. The enthalpy changes of PC 18 E 1 VE, PC 16 E 2 VE and PC 18 E 2 VE are higher than 100 J/g; on the contrary, it is 96 J/g for PC 16 E 1 VE. The enthalpy decrease is no more than 11% after 10 heating and cooling cycles. The 5 wt% mass loss temperatures of PC 18 E 1 VE, PC 16 E 2 VE and PC 18 E 2 VE are higher than 300 °C; on the contrary, it’s 283 °C for PC 16 E 1 VE. Using a weak polarity, flexible alkyl ether chain (-OCH 2 CH 2 O-) as a spacer to link the main chain and side chain is conducive to the crystallization of the alkyl side chain. These new phase change materials can be applied in heat storage, energy conservation, and environmental protection. [ABSTRACT FROM AUTHOR]

The free radical polymerization characteristics of various vinylated melamine derivatives, cross linking and linear, were analysed by GC/MS and HPLC/PDA measurements. Special attention was put on the general progress of the polymerization as well as on the opportunity for copolymerizations with common monomers like methyl methacrylate and styrene. In order to retrieve thermal properties of the (co)polymers also larger scale polymerizations have been done, showing that thermal stability can be increased by incorporation of vinylmelamines. Also the glass transition temperature can be increased linearly by increasing amounts of vinyl pentamethylmelamine in styrene and methyl methacrylate copolymers. [ABSTRACT FROM AUTHOR]

The present study demonstrates the hydrophobic effect of poly(electrolyte) multilayer films when they are alkyl-grafted and complexed or not with surfactants. For this purpose, sodium hydrophobically modified poly(acrylates) (PAC n Na, n = 10, 18) or their anionic complexes with alkyltrimethylammonium bromides (C x TAB, x = 10, 12, 14, 18), and the cationic poly(diallyldimethyldiammonium chloride) (PDDAMAC) are assembled by layer-by-layer deposition on a glass substrate. Contact angle (CA) measurements reveal that films constructed with PAC n Na-C x TAB/PDADMAC are superior water repellants than those of PACnNa/PDADMAC. For example, the highest CA is obtained for the PAC 18 Na-C 18 TAB/PDADMAC. Moreover, it has been observed that the CA increases with the alkyl chain length of PAC n Na and of surfactant. The film roughness and thickness have the same trend as wettability. Thinner and less coarse films are obtained by NaCl addition, as witnessed by SEM and AFM. [ABSTRACT FROM AUTHOR]

Four new vanadium oxyfluorides (VOFs), Sr4V3O5F13 (1), Pb7V4O8F18 (2), Pb2VO2F5 (3), and Pb2VOF6 (4), have been synthesized under mild hydrothermal conditions. The choice of starting reagents, AF2 or A(CH3CO2)2·xH2O (A = Pb, alkaline earth), determined the oxidation states of vanadium in the final products. The reaction of V2O5 with AF2 leads, consistently, to the formation of V(v) compounds, while the use of A(CH3CO2)2·xH2O results in V(iv) containing compounds, suggesting that the acetate species behaves as an effective mild reducing agent. The crystal structures, characterized by single crystal X-ray diffraction, revealed that the compounds exhibit various anionic VOF building blocks, including dimeric and trinuclear units, as well as one-dimensional chains. All compounds contain fluorine atoms that are not bonded to the vanadium atoms, which are located between two-dimensional layers consisting of corner- or edge-shared FA3 or FA4 polyhedra that separate the vanadium containing building blocks. The magnetic susceptibility data for 4 were measured as a function of temperature, yielding an effective magnetic moment of 1.72 μB that confirms the presence of V(iv). UV-vis reflectance and thermal properties were also characterized. [ABSTRACT FROM AUTHOR]

• Effect of replacing MgO by Nb 2 O 5 in the parent Na-Ca-P-Al-O glass system is studied. • Al suppresses Nb and accelerates Mg release process from the glasses into PBS. • Al and Mg addition decreases while Nb increases the polymerization of glass network. • Al and Nb contents control the glass transition temperature. • Glass thermal stability is highly correlated only with the Nb content. In vitro dissolution, structure, and thermal properties of the glass series Na 2 O-MgO CaO Nb 2 O 5 -Al 2 O 3 -P 2 O 5 were studied. The dissolution behavior in phosphate-buffered saline (PBS) confirmed the potential bioactive properties of tested glasses. The dissolution process was found to depend on the Al, Nb, and Mg contents. Al, respectively, suppresses the Nb and accelerates the Mg release process from the glasses. Moreover, Al stays highly bonded in the phosphate network during 14 days of immersion. In all glasses, the phosphate network was found to be highly disrupted and built mostly of Q1 units. Al and Mg addition decreases the polymerization of the glass network. The Nb addition effect was found to be the opposite. Thermal properties were correlated mostly with the Nb and Al contents. However, the fragility index of glasses increases with the content of P and Al. [ABSTRACT FROM AUTHOR]

ABSTRACT Two functional polysilsesquioxane microspheres, poly(epoxypropoxy)silsesquioxane (PESQ) and poly(epoxypropoxy/amino)silsesquioxane (PEASQ), were grafted onto commercial polylactic acid (PLA) via functional group reactions through melt processing and directly used as novel chain extenders to improve the thermal stability of PLA. During the whole reaction time of 35 min, the torques of P-2PESQ and P-1PEASQ were 60% higher than that of processed PLA. Thermal gravimetric analysis (TGA) revealed that the addition of PESQ or PEASQ into PLA increased the onset temperature for thermal degradation. PEASQ was found to be a potential chain extender for PLA. Compared with the processed PLA, the thermal decomposition temperatures of PEASQ modified PLA increased from 318 to 334°C at 5% weight loss. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41977. [ABSTRACT FROM AUTHOR]

A finite element numerical model is proposed in this paper to predict the effective thermal conductivity of polytetrafluoroethylene (PTFE) composites based on the Fourier’s law of heat conduction. The reliability of the numerical model is verified using the comprehensive experimental results and theoretical models presented by predecessors. A systematic study is conducted through numerical simulation to examine the impact of graphite particle size, volume fraction, and distribution style on the thermal conductivity of PTFE composites. A prediction model of the thermal conductivity of carbon fibers reinforced PTFE composites is introduced. The results of the prediction model agree well with experimental data. A trade off between the volume fractions of graphite particles and carbon fibers is conducted. And the optimum volume fraction matching is 17.76 and 10% for graphite particles and carbon fibers, respectively. [ABSTRACT FROM AUTHOR]

ABSTRACT Three types of zinc salts, ZnAl2O4, ZnFe2O4, and Zn2SiO4, were prepared by coprecipitation. Potential smoke and toxicity suppression by zinc salts in flame-retardant polyurethane-polyisocyanurate foams (FPUR-PIR) with dimethylmethylphosphonate (DMMP) and tris (2-chloropropyl) phosphate (TCPP) were investigated. The crystal structure and dispersity of zinc salts in FPUR-PIR were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Smoke density, flame retardancy, and thermal degradation were studied using smoke density rating (SDR), limiting oxygen index (LOI), the cone calorimeter test, and thermogravimetry coupled with FTIR spectrophotometry (TGA-FTIR). The results indicated that pure zinc salts were obtained and evenly dispersed on the cell wall of FPUR-PIR. SDR and the specific extinction area (SEA) were significantly decreased, the time to second heat release rate peak (pk-HRR) of FRUP-PIR was delayed after incorporation of the zinc salts; zinc salts partially inhibited phosphorus oxide release into the gas phase, enhanced the condensed phase effect of phosphorus, reduced, and prolonged the release of isocyanate compound and hydrogen cyanide from FRUP-PIR; due to an increase in the amount of char residues, which indicated the suppression of smoke and toxicity volatiles. ZnFe2O4 resulted in better char formation at the initial degradation stage of FPUR-PIR, and ZnAl2O4 retained more phosphorus in the solid phase at higher temperature. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41846. [ABSTRACT FROM AUTHOR]

ABSTRACT A series of new segmented semifluorinated polyaryl ethers (PAEs) containing a biphenyl segmented by semifluorinated oligoethylene (SFE) units were prepared by nucleophilic addition of a commercial oligo(ethylene glycol)s to 4,4′-bis(4-trifluorovinyloxy)biphenyl. These new thermoplastics were characterized by 1H and F19 nuclear magnetic resonance (NMR) and attenuated total reflectance Fourier transform infrared (ATR-FTIR). Gel permeation chromatography (GPC) analysis displayed number average molecular weights ( Mns) from 9000 to 13,000. Thermal properties of the polymers were studied by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). DSC chromatograms displayed glass transition temperatures ( Tgs) from 11 to 1°C. The onsets of degradations were observed by TGA analysis between 313 to 333°C in air and 326 to 363°C in nitrogen, respectively. A second onset of degradation was observed from 452 to 470°C for all polymers. In addition, crystalline morphologies were studied by tapping mode atomic force microscopy (TM-AFM) and showed needle-like crystallites. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41798. [ABSTRACT FROM AUTHOR]

Abstract: A comprehensive survey of the recent developments on the synthesis, properties and applications of silicone containing copolymers is provided. Influence of ( R2Si O ) backbone composition on the physicochemical properties of silicone copolymers, such as thermal transitions, solubility parameter and surface tension is discussed. Preparation and properties of well-defined α,ω-reactive organofunctionally terminated (telechelic) silicone oligomers and their utilization in the preparation of a wide range of block and segmented copolymers through step-growth, anionic, ring-opening and living free-radical polymerization techniques are provided. Use of silicone oligomers in the modification of polymeric network structures is also discussed. Special emphasis is given to the discussion of the effect of silicone oligomer and organic segment structure and molecular weight on the morphology and surface and bulk properties of the resultant silicone containing copolymers and networks. [Copyright &y& Elsevier]

ABSTRACT The cationic polymerization of dimethylketene is achieved in dichloromethane at −30 °C, using a stoichiometric mixture of aluminum bromide (AlBr3) and tetra- n-butylammonium bromide ( n-Bu4N+Br−) as initiator. Characterizations by 1H and 13C NMR show that the resulting polymers have a perfect polyketonic microstructure. Capillary viscosity, DSC, and SEC analysis show that for a constant monomer/initiator ratio, polymers synthesized in the presence of tetra- n-butylammonium bromide are more crystalline and have better properties than those produced only with AlBr3. Melting temperatures, inherent viscosities and average molecular weights are systematically higher. A good linearity is observed between ln (inherent viscosity) versus ln [ABSTRACT FROM AUTHOR]

ABSTRACT A thermally cured epoxy-siloxane hybrid material that is curable at low temperature (L-expoxy hybrimer) was investigated for use as an LED encapsulant. This new hybrimer was fabricated using thermally initiated, cationic polymerization of cycloaliphatic epoxy oligosiloxane (CAEO) resin, derived from non-hydrolytic sol -gel, mixed with oxetane hardener in the presence of a hexafluoroantimonate-type thermo-cationic initiator. The L-epoxy hybrimer was cured at a lower temperature (below 120 °C) than previously reported for an epoxy hybrimer with anhydride hardener (above 180 °C). The L-epoxy hybrimer showed high thermal resistance to yellowing under long-term high temperature condition, and maintained good optical transmittance. Also, it had a high refractive index (up to 1.57), as well as the hardness (Shore D 80), and low water-vapor permeability, when the new hybrimer was used to encapsulate an LED, it showed good adhesion without cracks or delamination and maintained their initial performance after the long-term aging tests (120 and 85 °C at 85% humidity). © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014, 131, 39968. [ABSTRACT FROM AUTHOR]

ABSTRACT The benzoxazines of three naturally occurring phenylpropanoid phenols: ferulic, coumaric, and phloretic acids, and their esters are described. Benzoxazines with conjugated unsaturated chains exhibit unusual poor thermal stability and degrade partially at the polymerization temperature making necessary the use of a catalyst (BF3.Et2O) to low the polymerization temperature and prevent degradation. Polybenzoxazines are prepared thermally and characterized by DSC and TGA techniques. The resulting materials have superior Tgs when compared with those prepared from an unsubstituted monofuctional benzoxazine due to the additional crosslinking through the ester and carboxylic moieties. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4894-4903 [ABSTRACT FROM AUTHOR]

Abstract: Poly [2-(cinnamoyloxy)ethyl methacrylate-co-octamethacryl-POSS] nanocomposites were synthesized from octamethacryl-POSS and 2-(cinnamoyloxy)ethyl methacrylate (CEM) by free radical polymerization. The chemical structures and morphologies of these nanocomposites were determined by FTIR, 29Si NMR, energy-dispersive spectroscopy (EDS), X-ray powder diffraction (XRD), and scanning electron microscopy (SEM) techniques. The XRD data showed that the materials were amorphous in nature, indicating that POSS formed an aggregate instead of a crystalline form in the polymer matrix. The POSS-CEM nanocomposites exhibited high thermal stability. Excitation and emission of the CEM-incorporated POSS nanocomposites, studied in the solid state, exhibited blue emission with CIE (x, 0.178; y, 0.137) coordinates, in addition to an emission intensity that increased with increasing CEM (monomer) concentration. [Copyright &y& Elsevier]

This investigation reports a comparative study of poly(2-ethylhexyl acrylate) (PEHA) prepared via atom transfer radical polymerization (ATRP), reverse atom transfer radical polymerization (RATRP) and conventional free radical polymerization (FRP). The molecular weights and the molecular weight distributions of the polymers were measured by gel permeation chromatography (GPC) analysis. Structural characterization of the polymers was carried out by H NMR and MALDI-TOF-MS analyses. Thermal properties of the polymers were evaluated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The polymerization results and the thermal properties of PEHAs prepared via ATRP, RATRP and FRP were compared. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

ABSTRACT Structural isomers of thermo-oxidatively stable poly(carborane-siloxane-arylacetylene) (PCSAA), namely, m-PCSAA and p-PCSAA, were synthesized by the reaction of the dimagnesium salts of m-diethynylbenzene or p-diethynylbenzene with 1,7-bis(chlorotetramethyldisiloxyl)- m-carborane. The developed polymers have exceptional thermo-oxidative properties similar to their diacetylene counterpart poly(carborane-siloxane-acetylene), PCSA. Thermal treatment of either of the PCSAAs results in a fully crosslinked thermoset by 500 °C resulting from the cycloaddition reactions involving the acetylene and aryl functionalities and subsequent formation of bridging disilylmethylene entities as discerned from Fourier transform infrared, 13C and 29Si solid-state NMR, and XPS studies. X-ray diffraction analysis revealed that the thermosets obtained from p-PCSAA possess enhanced crystallinity when compared to that obtained from m-PCSAA possibly due to more efficient packing interactions of the p-diethynylbenzene groups during thermoset formation. The presence of the aryl groups in the backbone of the PCSAAs' chains appeared to have enhanced the storage and bulk moduli of their thermosets when compared to the thermoset of PCSA. Dielectric studies of m-PCSAA and p-PCSAA revealed segmental relaxation peaks, α, above their glass transition temperatures with p-PCSAA exhibiting a broader peak with a slower relaxation rate than m-PCSAA. © 2013 Wiley Periodicals, Inc.† J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2638-2650 [ABSTRACT FROM AUTHOR]

In this work, we studied the thermal characterization of block copolymers based on ε-caprolactone. The copolymers were obtained by anionic polymerization techniques, using different co-monomers such as styrene (S) and dimethylsiloxane (DMS). Synthesized copolymers were characterized by H-nuclear magnetic resonance, size exclusion chromatography, and Fourier transform infrared spectroscopy. Isothermal crystallization was performed by differential scanning calorimetry (DSC), and Avrami's theory was employed in order to obtain kinetics parameters of interest, such as the half-life for the crystallization process ( t), the bulk crystallization constant ( k), and the Avrami's exponent ( n). The spherulitic growth was measured by polarized optical microscopy in order to determine the crystallization behavior. Poly(ε-caprolactone) block (PCL) crystallization was analyzed by considering the physico-chemical characteristics of the neighboring block, PS or PDMS. The chemical nature of the neighbor block in the PCL-based copolymer affects the kinetics parameters of Avrami's equation, as can be deduced by comparing the values obtained for pure PCL and the studied block copolymers. On the other hand, the apparent thermal degradation activation energies E for PCL and block copolymers were determined by Ozawa's method. The incorporation of PDMS instead of PS improves the stability of the resulting copolymer, as it was observed by thermogravimetric analysis. [ABSTRACT FROM AUTHOR]

Abstract: The paper reports the synthesis of new silsesquioxanes with methacrylate and/or vinyl units, obtained by combining the sol–gel technique with radical polymerization in the presence of 2,2′-azobis(2-methylpropionitrile) as initiator and a cationic surfactant, cetyltrimethylammonium bromide. The thermal behaviour was investigated through simultaneous thermogravimetric and differential scanning calorimetry analysis (TG/DSC) coupled on-line with Fourier transform infrared spectroscopy (FTIR) and mass spectrometry (MS), as well as by pyrolysis and gas chromatography–mass spectrometry (GC–MS). The aim of the investigation consists in drawing useful information on the influence of both chemical structure and chain end double bonds and silanol units on the resistance of such compounds against thermal degradation. [Copyright &y& Elsevier]