•By nucleating agent and erasing thermo-history α and β crystal grow simultaneously.•The growth rates of α and β form were compared under the same Tc and Tm0.•The growth rate of β form is faster than that of α form for both sPS and BzsPS-2%.•BzsPS containing rigid comonomer is more favourable for α form comparing to sPS.•sPS with 5% benzoylation only form α form crystal below 225 °C.The crystallization behaviour of syndiotactic polystyrene (sPS) and benzoylated sPS (BzsPS) was investigated by POM, DSC and XRD. The results suggest β form of sPS has higher equilibrium melting temperature Tm0 and the fold surface free energy σe than α form. With increasing benzoylation degree the growth rates and Tm0 of two forms decrease, but their Tm0 decrement is very close; the σe of β form more increases than that of α form, the formation of α is more favourable. Upon loading trace amount of α nucleating agent PTBBNa in samples the growth rate of two forms can be strictly compared in the same melting and crystallization temperature condition, the results reveal that the growth rate of β form is faster than that of α form in sPS and BzsPS-2%. Using supercooling degree ΔT and σe two parameters has explained the formation competition mechanism of α and β forms.Loading trace amount of α heterogeneous fibrous nucleating agent PTBBNa in sPS and benzoylated sPS is a good way to investigate strictly the linear crystal growth rate of α and β forms under the same melt condition and the same crystallization temperature range. The results reveal that the trace amount of α nucleating agent PTBBNa loading in samples does not influence the growth rate of α and β forms and the growth rate of β form is faster than that of α form in both sPS and BzsPS-2% (with benzoylation degree of 2%) samples.

Interfacial thermal conductance (ITC) receives enormous consideration because of its significance in determining thermal performance of hybrid materials, such as polymer based nanocomposites. In this study, the ITC between sapphire and polystyrene (PS) was systematically investigated by time domain thermoreflectance (TDTR) method. Silane based self-assembled monolayers (SAMs) with varying end groups, -NH2, -Cl, -SH and -H, were introduced into sapphire/PS interface, and their effects on ITC were investigated. The ITC was found to be enhanced up by a factor of 7 through functionalizing the sapphire surface with SAM, which ends with a chloride group (-Cl). The results show that the enhancement of the thermal transport across the SAM-functionalized interface comes from both strong covalent bonding between sapphire and silane-based SAM, and the high compatibility between the SAM and PS. Among the SAMs studied in this work, we found that the ITC almost linearly depends on solubility parameters, which could be the dominant factor influencing on the ITC compared with wettability and adhesion. The SAMs serve as an intermediate layer that bridges the sapphire and PS. Such a feature can be applied to ceramic-polymer immiscible interfaces by functionalizing the ceramic surface with molecules that are miscible with the polymer materials. This research provides guidance on the design of critical-heat transfer materials such as composites and nanofluids for thermal management.Keywords: interfacial thermal conductance; miscibility; organic−inorganic interface; solubility parameter; time domain thermoreflectance

In polymer-based electric microdevices, thermal transport across polymer/ceramic interface is essential for heat dissipation, which limits the improvement of the device performance and lifetime. In this work, four sets of polystyrene (PS) thin films/sapphire samples were prepared with different interface adhesion values, which was achieved by changing the rotation speeds in the spin-coating process. The interfacial thermal conductance (ITC) between the PS films and the sapphire were measured by time domain thermoreflectance method, and the interfacial adhesion between the PS films and the sapphire, as measured by a scratch tester, was found to increase with the rotation speed from 2000 to 8000 rpm. The ITC shows a similar dependence on the rotation speed, increasing up to a 3-fold from 7.0 ± 1.4 to 21.0 ± 4.2 MW/(m2 K). This study demonstrates the role of spin-coating rotation speed in thermal transport across the polymer/ceramic interfaces, evoking a much simpler mechanical method for tuning this type of ITC. The findings of enhancement of the ITC of polymer/ceramic interface can shed some light on the thermal management and reliability of macro- and microelectronics, where polymeric and hybrid organic–inorganic nano films are employed.Keywords: interfacial adhesion; interfacial thermal conductance; polymer thin film; spin-coating; time domain thermoreflectance

The polyamide 66 (PA66)/lanthanum acetate blends with small amounts of salt loadings (≤ 1 wt% of PA) have been prepared in a twin-screw extruder. The rheology of PA66 and its blends has been investigated by a rotational rheometer. The results suggested that with the salt loading in excess of 0.2 wt% the typical Newtonian viscosity plateau disappeared and both the low-frequency complex viscosities η* and storage modulus G′ of blends were much higher than those of neat PA66, the storage modulus was higher than the loss modulus at low frequencies (tanδ < 1), i.e., the melt changed from a viscoelastic liquid for unfilled polymer to a viscoelastic solid (G′ > G″). While the viscosity followed a strong shear thinning with increasing frequency, the η* and G′ decreased significantly even lower than those of neat PA66 at high frequencies. The combination of dynamic mechanical analysis (DMA) and X-ray photoelectron spectroscopy (XPS) analysis has revealed that coordination effect occurred between lanthanum and carbonyl oxygen atoms in amide groups of the polymer to form pseudocrosslinked network structure, which makes the glass transition temperatures (Tg) and storage modulus (E′) of blends enhanced. The network structure formation-destruction and chains entanglement-disentanglement processes at different frequencies are responsible for the above rheological behaviors of blends.

In the present work, a surfactant, the phosphoric ester of poly(ethylene oxide) (10) nonylphenyl (abbreviated as NP-10P throughout the paper), was incorporated into poly(propylene carbonate) (PPC) by melt-blending. Characterization data by TGA and Py-GC/MS have suggested that the obtained PPC/NP-10P complex displays excellent thermal stability compared to pure PPC. The thermal decomposition temperature, with a 5% loss in weight, increases by about 103 °C from 180 °C for PPC to 283 °C for PPC with 15 wt% NP-10P. Furthermore, with only 1 wt% of NP-10P incorporated into the PPC, an increase of about 74 °C in the decomposition temperature is found. The pyrolysis mechanism of PPC before and after modification with NP-10P varies from chain unzipping degradation to chain random scission followed by unzipping degradation. The results of 31P NMR, FTIR and intrinsic viscosity measurements have illustrated that the PPC is end-capped with NP-10P, which leads to the improvement of thermal stability and the change in pyrolysis mechanism of PPC. Moreover, this new finding will facilitate development and widespread applications of this biodegradable material.

Superhydrophobic surfaces were prepared by poly(methyl methacrylate) (PMMA) or polystyrene (PS) modification on an optimized anodic aluminum oxide (AAO) honeycomb-like structure surface. The AAO membrane was initially etched in sodium hydroxide solution to get a hierarchical polygon-cavity structure in micro- and nano-scales, and then, it was coated with the polymer solution. The obtained polymer-modified AAO films show superhydrophobicity with water contact angles of larger than 150°. The intrinsic contact angles of the PMMA and PS are 68° and 94°, respectively. The morphology and components of the micro-/nano-structure were characterized by SEM and XPS, respectively, and the mechanism is discussed. This work provides a simple method to obtain superhydrophobic surfaces by common polymers without the need for low surface energy compounds.

In order to improve the thermal stability of δe form of sPS that possesses nanoporous structure, benzoylation of the phenyl groups was adopted and performed by solution procedure or solid procedure. The solution procedure involves initial benzoylation of sPS in solution and then preparing δe form by solvent induction of benzoylated sPS; the solid procedure means benzoylation of δe form of sPS in solid state. Usual modifications of sPS by solution procedure greatly decrease the crystallinity of the nanoporous related δe form. In this work, sPS can well maintain its crystallinity of δe form after benzoylation by solution procedure, even when benzoylation degree reaches 20%. Thermally induced phase transition behaviors of corresponding δe form were investigated by Differential scanning calorimeter and temperature-dependent X-ray diffraction analysis. The results show that the δe–γ transition temperature increases after benzoylation by both two procedures, indicating improved thermal stability of δe form. The subsequent γ–α transition and the melting of α form both shift to lower transition temperature. Meanwhile, the transition of δe form to γ form was prohibited by solution procedure contrast to solid procedure.

A shape memory polymer film with a stable micro/nano-fibrous structure is prepared via electrospinning of a triethoxysilane end-capped precursor solution, followed by crosslinking. The fibrous structure is stable and reversible for at least three cycles of shape memory tests. The electrospun SMP film also exhibits consistently faster recovery than the bulk film.

An organogelator based on 4,4′-diaminodiphe-nylmethane was synthesized facilely and its gelation ability was evaluated in various organic solvents. It gelated in 11 of 15 organic solvents tested herein, loading 3.0 wt%, indicating that it possesses a versatile gelation ability. TEM observations of its aggregation mode of xerogel in different solvents showed that it assembled into a rod-shaped morphology, a rolled-lamellar morphology, a spherical-like pearl necklace morphology, and a tubular morphology in dimethylformamide, dimethylsulfoxide, xylene, and 1-butanol, respectively. sol–gel polymerization of tetraethoxysilane was carried out in these gel systems. The TEM and SEM pictures of nanometer-level silica took on morphologies analogous to those of the organogels. The composition of nanostructured sintered SiO2 mainly consisted of Si and O through a scanning electron microscope SEM equipped with energy-dispersive x-ray spectroscopy. The supermolecular aggregation mode of the organogelator varied in different organic solvents. Multimorphologic nanostructured SiO2 materials were prepared through a sol–gel transcription with the simple-structure bis-(4-stearoylaminophenyl)methane as template in the different solvents.

In order to evaluate the toxicity of TiO2 particles, the acute toxicity of nano-sized TiO2 particles (25 and 80 nm) on adult mice was investigated compared with fine TiO2 particles (155 nm). Due to the low toxicity, a fixed large dose of 5 g/kg body weight of TiO2 suspensions was administrated by a single oral gavage according to the OECD procedure. In 2 weeks, TiO2 particles showed no obvious acute toxicity. However, the female mice showed high coefficients of liver in the nano-sized (25 and 80 nm) groups. The changes of serum biochemical parameters (ALT/AST, LDH) and pathology (hydropic degeneration around the central vein and the spotty necrosis of hepatocytes) of liver indicated that the hepatic injury was induced after exposure to mass different-sized TiO2 particles. In addition, the nephrotoxicity like increased BUN level and pathology change of kidneys was also observed in the experimental groups. The significant change of serum LDH and alpha-HBDH in 25 and 80 nm groups showed the myocardial damage compared with the control group. However, there are no abnormal pathology changes in the heart, lung, testicle (ovary), and spleen tissues. Biodistribution experiment showed that TiO2 mainly retained in the liver, spleen, kidneys, and lung tissues, which indicated that TiO2 particles could be transported to other tissues and organs after uptake by gastrointestinal tract.

The rising commercial use and large-scale production of engineered nanoparticles (NPs) may lead to unintended exposure to humans. The central nervous system (CNS) is a potential susceptible target of the inhaled NPs, but so far the amount of studies on this aspect is limited. Here, we focus on the potential neurological lesion in the brain induced by the intranasally instilled titanium dioxide (TiO2) particles in rutile phase and of various sizes and surface coatings. Female mice were intranasally instilled with four different types of TiO2 particles (i.e. two types of hydrophobic particles in micro- and nano-sized without coating and two types of water-soluble hydrophilic nano-sized particles with silica surface coating) every other day for 30 days. Inductively coupled plasma mass spectrometry (ICP-MS) were used to determine the titanium contents in the sub-brain regions. Then, the pathological examination of brain tissues and measurements of the monoamine neurotransmitter levels in the sub-brain regions were performed. We found significant up-regulation of Ti contents in the cerebral cortex and striatum after intranasal instillation of hydrophilic TiO2 NPs. Moreover, TiO2 NPs exposure, in particular the hydrophilic NPs, caused obvious morphological changes of neurons in the cerebral cortex and significant disturbance of the monoamine neurotransmitter levels in the sub-brain regions studied. Thus, our results indicate that the surface modification of the NPs plays an important role on their effects on the brain. In addition, the difference in neurotoxicity of the two types of hydrophilic NPs may be induced by the shape differences of the materials. The present results suggest that physicochemical properties like size, shape and surface modification of the nanomaterials should be considered when evaluating their neurological effects.Highlights► We compare the potential neurotoxicity of four different types of TiO2 particles in vivo. ► TiO2 nanoparticles pose greater neurotoxicity than the larger counterpart. ► Hydrophilic TiO2 nanoparticles are more toxic than the hydrophobic ones with similar size. ► Shape difference of nanoparticles may induce different neurotoxicity. ► The physicochemical properties of nanomaterials such as size, shape and surface modification should be considered when evaluating their neurological effects.

A shape memory polymer film with a stable micro/nano-fibrous structure is prepared via electrospinning of a triethoxysilane end-capped precursor solution, followed by crosslinking. The fibrous structure is stable and reversible for at least three cycles of shape memory tests. The electrospun SMP film also exhibits consistently faster recovery than the bulk film.