Fluxgate magnetorelaxometry of superparamagnetic nanoparticles for hydrogel characterization

A new characterization method for hydrogels based on the relaxation behavior of superparamagnetic nanoparticles (MNPs) is proposed. MNPs are incorporated in the hydrogel to examine its network properties. By analyzing their relaxation behavior, incorporated and mobile nanoparticles can be studied. In the case of mobile nanoparticles, the microviscosity of the hydrogel can be determined. Thus, this method allows the studying of gelation as well as the degradation process of hydrogels. Furthermore, the hydrogel can have any shape (e.g. microspheres or larger blocks) and no sample preparation is needed, avoiding artefacts.     

A facile method to prepare polypropylene/poly(butyl acrylate)alloy via water–solid phase suspension grafting polymerization

Polypropylene/poly(butyl acrylate) alloy is produced by water–solid phase suspension grafting polymerization with a submicrometer microdomain where graft polymerization occurs within micropores of polypropylene particles prepared by reactor granule technology(RGT). The results show that the grafting percentage(GP) of butyl acrylate(BA) increases with the increase of the monomer concentration, which could reach 32.6% while the grafting efficiency(GE) is up to 98%. The addition of the crosslinking agent, triethylene glycol diacrylate(TEGDA), could improve GP up to 36.3%. Transmission electron microscopic(TEM) micrographs demonstrate that PBA microdomains distributed in PP matrix increase in size less than 500 nm. Moreover, TEM images show that the grafting phase exhibits a singlephase behavior with the addition of TEGDA, which implies that the ratio of graft copolymer increased.     

Transparent room temperature cured elastomers based on bisphenol A

The synthesis of a divinyl‐terminated resin from commercially available bisphenol A and polymerization with silane containing compounds utilizing a room temperature hydrosilylation reaction is demonstrated. The transparent, clear polymers exhibit excellent thermal and oxidative stability while maintaining elastomeric properties and good hardness. These polymers also have the ability to be dyed any color in the spectrum. Published 2013. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 523–526     

序列式含芴季铵化聚芳醚砜阴离子交换膜的制备及交联改性

为得到具有高电导率和稳定性的阴离子交换膜,采用两步聚合法合成了含芴的序列式聚芳醚砜,经付克氯甲基化、季铵化及碱化制备了季铵化聚芳醚砜,并以脂肪族二胺(N,N,N′,N′-四甲基丙二胺(TMPDA)及N,N,N′,N′-四甲基己二胺(TMHDA))为交联剂,通过直接交联及后交联法分别制备了2类序列交联型阴离子交换膜.制得的膜材料离子交换容量为1.59~2.12 mmol/g,柔韧结实.与具有相似离子交换容量的非交联膜相比,交联膜的抗溶剂性能、尺寸稳定性、离子电导率等性能均得到了提高.交联膜在高温水中的水解稳定性、强碱性条件下的化学稳定性显著增强.探讨了直接浇铸交联处理及成膜后交联处理2种交联方式对膜性能的影响,结果表明,后交联处理可以有效避免浇膜过程凝胶的形成,而且膜的稳定性相对于未交联膜有大幅度提高.尤其以TMHDA为交联剂的后交联膜的各项性能均优于相应非交联膜,IEC为2.17 mmol/g的PCL-M(H)膜,在30°C时吸水率为99%,膜径向尺寸变化率为15%,电导率为23.8 mS/cm,90°C时电导率达到82 mS/cm,经过4 mol/L的NaOH溶液室温处理240 h后,离子电导率损失为7.6%,100°C水处理24 h后重量损失为5.1%,表现出较好的稳定性.     

Side Reactions in the Formation of Polyurethanes: Model Reactions Between Phenylisocyanate and 1-Butanol

The following side reactions occurring in the formation of polyurethanes were modeled: a reaction of excess phenyl isocyanate either with 1-butanol in 1, 4-dioxane and in bulk, or with n-butylphenyl urethane or water in dioxane catalyzed with dibutyltin dilaurate that leads to the formation of n-butyl-α, γ-diphenyl allophanate N, N-diphenylurea, and 1, 3, 5-triphenylbiuret. The reaction products were determined quantitatively by means of liquid chromatography. The rate and equilibrium constants were calculated at various temperatures and various initial ratios of functional groups. Biuret is formed from N, N'-diphenylurea much more quickly than allophanate from urethane, and the equilibrium constant of its formation is also higher.     

Effect of the Shell Crosslinking Level andCore/Shell Ratio on the Morphology of LatexParticles in the Preparation of Hollow Latexes简

Three-layer core/shell latex particles with various shell crosslinking level and shell thickness were prepared by multistep emulsion polymerization, and the hollow latex particles with different morphologies were then obtained after alkali post-treatment. Influences of divinyl benzene(DVB) content and the core/shell mass ratio on emulsion polymerization and particle morphology were investigated. Results showed that with the increase of DVB content, the percentage of total amount of ―COOH on the particle surface and free in aqueous phase(PSFa) decreased, and the morphology of the post-treated particles underwent evolution from cracked, intact hollow to deficient swelling structure. Decreasing the core/shell mass ratio could not only make more carboxyl groups encapsulated by the shell, but also increase the shell resistance to the swelling of the core. The uniform hollow latex particles with intact morphology were obtained when the DVB content was 3.54 wt% and the core/shell mass ratio was 1/6.     

Asphalt modification with different polyethylene-based polymers

Several polyethylene and polyethylene-based copolymers were used to modify a 70/100 penetration grade asphalt from vacuum distillation. The morphological and storage stability analyses showed that, in all cases, the obtained materials were strongly biphasic and tended to separate into polymer-rich and asphalt-rich phases. However, among the tested polymers, a linear low-density polyethylene allowed for the preparation of a mix that had strongly enhanced mechanical properties, with respect to those of the base asphalt. Mixes with different percentages of this polymer were, therefore, prepared and studied from a rheological point of view, both in the range of small and large deformations. The analysis showed that, in spite of its insolubility, the polymer spread continuously through the asphalt matrix and that the obtained properties can probably be ascribed to the formation of a very low extent of crosslinking between the polymer chains.     

Effect of hydrogen bonds on intermolecular crosslinking reaction by introduction of carboxyl groups in free-radical crosslinking monomethacrylate/dimethacrylate copolymerizations

The effect of physical interaction through hydrogen bonds on the intermolecular crosslinking reaction leading to the promoted gelation in free-radical crosslinking monovinyl/divinyl copolymerizations was discussed from the standpoint of the control of network formation. The solution copolymerizations of benzyl methacrylate (BzMA) with 2 mol% of 1,6-hexanediol dimethacrylate in t-butylbenzene were conducted in the absence and presence of different amounts of mono(2-methacryloyloxyethyl) succinate (MMOES). Gelation was promoted by the addition of MMOES and the ratio of the actual gel point to the theoretical one became smaller; this would be related to the formation of hydrogen bonds between carboxyl groups introduced into prepolymer and growing polymer radical. As an extension of the above discussion, we treated the effect of hydrogen bonds on the gelation in the crosslinking BzMA/triicosaethylene glycol dimethacrylate copolymerization. The addition of MMOES obviously promoted the gelation. The ratio of the actual gel point to the theoretical one calculated according to Stockmayer's equation [J. Chem. Phys. 12 (1944) 125] was obtained as 1.9, very close to unity.     

Thermal and shrinkage behaviour of stretched peroxide-crosslinked high-density polyethylene

The thermal shrinkage of stretched crosslinked high-density polyethylene (HDPE) was investigated with the aim to produce heat shrinkable materials. The heat shrinkable property was achieved by a process of heating-stretching-cooling by aid of tensile machine on crosslinked HDPE obtained by compounding with various amount of peroxide. Effect of stretching ratio and stretching temperature on thermal and shrinkage behaviour at varying peroxide contents was investigated. The results showed that crosslinking hindered the crystallization process by decreasing the melting and crystallization temperatures as well as the total degree of crystallinity. The stretching ratio had no significant effect on shrink temperature but rather on ultimate shrinkage. The stretching temperature had relatively significant influence on the shrink temperature. Crosslinked HDPE stretched at above melting point (140 °C) had higher shrink temperature as compared to those stretched at lower temperature (90 °C). These effects could be reasonably explained by Hoffman theory and changes in crystallites size and total amount of crystallinity.     

Phosphorus-containing thermosets obtained by cationic copolymerisation of glycidyl compounds with a spiroorthoester or γ-butyrolactone

The synthesis of a bis[(1,4,6-trioxaspiro[4.4]nonan-2-yl)-methyloxy] ethane (bisSOE) and its copolymerisation with mixtures of diglycidyl ether of bisphenol A (DGEBA) and different phosphorus-containing glycidyl compounds led to materials with enhanced flame retardancy and low shrinkage on crosslinking. Analogous materials were obtained by reaction of mixtures where the spiroorthoester (SOE) is formed in the reaction medium from γ-butyrolactone and a diglycidyl compound.The incorporation of phosphorus in the networks increases the LOI values and all crosslinked polymers showed a slight shrinkage after curing, much lower than that observed in conventional epoxy resins. The materials from preformed SOE showed lower shrinkage than the analogues from lactone and epoxy groups.