In Situ Preparation of a Compatibilized Poly(cis‐1,4‐butadiene)/Poly(ε‐caprolactone) Blend

The ternary Ziegler‐Natta‐type catalyst system based on neodymium versatate (NdV), diisobutylaluminium hydride (DIBAH) and ethylaluminium sesquichloride (EASC) was used for the in situ preparation of a compatibilized blend consisting of poly(cis‐1,4‐butadiene) (BR = butadiene rubber) and poly(ε‐caprolactone) (PCL). Poly(cis‐1,4‐butadiene)‐block‐poly(ε‐caprolactone) which acts as compatibilizer for the two immiscible polymers BR and PCL was obtained by a two step sequential polymerization with the preparation of a living cis‐1,4‐BR building block in the first stage and the subsequent polymerization of CL during the second stage. This preparation method resulted in a polymer blend comprising the homopolymers BR and PCL as well as the block copolymer BR‐block‐PCL. For detailed characterization the block copolymer was separated from the respective homopolymers BR and PCL by means of fractionation with the binary solvent mixture dimethylformamide/methylcyclohexane (DMF/MCH) which mixes well at elevated temperature and exhibits phase separation at ambient temperature. ¹H NMR, IR, SEC and TEM were used for characterization of the block copolymer.

TEM of BR‐block‐PCL.     

Long‐Aliphatic‐Segment Polyamides: Salt Preparation and Subsequent Anhydrous Polymerization

Long‐aliphatic‐segment polyamides were prepared based on hexamethylenediamine and α,ω‐(CH₂)_x biosynthetic diacids (x = 10, 11, 12). The pertinent monomers (salts) were isolated as solids, thoroughly characterized for the first time, and then submitted to an anhydrous melt prepolymerization technique. The obtained prepolymers exhibited in the range of 5 100–11 800 g · mol^?1, and the molecular weight was further increased by up to 55% through solid‐state finishing. The suggested overall polyamidation cycle was conducted at short melt‐reaction times, so as to avoid any thermal degradation, and was proved efficient, indicating similar reactants polymerizability independently of the methylene content.

     

Kinetics of Cationic Photopolymerizations of UV‐Curable Epoxy‐Based SU8‐Negative Photoresists With and Without Silica Nanoparticles

Summary: This paper reports on the photocuring kinetics of protonic‐acid‐initiated cationic polymerizations of UV‐curable epoxy‐based SU8‐negative photoresist systems with and without silica nanoparticles, as assessed using photo‐DSC, FTIR spectroscopy, UV‐vis spectroscopy, and SEM. Photo‐DSC analysis using an autocatalytic kinetic model demonstrated that the cross‐link density and cure rate increased as the concentration of silica nanoparticles with surface silanol groups increased to 2.5 wt.‐%. This result was confirmed by FTIR spectroscopy, and suggests that the presence of silica nanoparticles of up to 2.5 wt.‐% promoted the cure conversion and cure rate of the UV‐curable hybrid organic/inorganic negative photoresists due to the synergistic effect of silica nanoparticles acting both as an effective flow or diffusion‐aid agent and as a proton‐donor cocatalyst during the cationic photopolymerization process. The decrease in the cross‐link density that occurred when the silica content was higher than 2.5 wt.‐% was attributed to aggregation between silica nanoparticles due to their high surface energy.

SEM photograph at the film‐air interface of the UV‐cured hybrid organic/inorganic photoresist containing 10 wt.‐% silica nanoparticles.     

Study on the Curing Process and the Gelation of Epoxy/Anhydride System for No‐Flow Underfill for Flip‐Chip Applications

No‐flow underfill is used in the assembly of microelectronics to increase the productivity and to decrease the cost of the flip‐chip manufacturing. The curing process, especially the gelation of the no‐flow underfill, is essential for the yield and reliability of the flip‐chip assembly. A differential scanning calorimeter (DSC) and a stress rheometer are used to study the curing process of epoxy/anhydride system at different curing rates and different isothermal temperatures. The gel point is found when the storage modulus and the loss modulus of the resin measured by the rheometer equals to each other. The degree of cure (DOC) at gelation is calculated according to the results from DSC. The results indicate a strong dependence of the DOC at gelation on the heating rates and the curing temperatures. In order to further investigate the difference in the curing process at various heating rates, FTIR spectra of the resin are taken during curing. The change of different functional groups is recorded and compared. The results do not show a significant difference in the chemical structure at different heating rates. The early gelation at high heating rate/ high temperature can be caused by the structure difference in the epoxy network at the early stage of curing due to the chain initiation and propagation of the molecules in the curing process.

Dependence of gelation of the sample on the isothermal temperatures.     

Effect of High‐Energy Vibromilling on Interfacial Interaction and Mechanical Properties of PVC/Nano‐CaCO3 Composites

Summary: The effects of interfacial interaction between nano‐CaCO₃ and PVC on mechanical properties and morphology of PVC/nano‐CaCO₃ composites were studied. Nano‐CaCO₃ was treated with vibromilling in the presence of PVC and coupling agents. The mechanical properties of PVC/treated nano‐CaCO₃ are remarkably improved. Transmission electron microscopy results revealed that vibromilled nano‐CaCO₃ particles are well dispersed in PVC matrix with good homogeneity and well adhered to PVC matrix. Molau test indicated that chemical reaction between newly formed surface of nano‐CaCO₃ and PVC or coupling agent took place. Theoretical calculation results show that the interfacial interaction between PVC and nano‐CaCO₃ are substantially improved through vibromilling treatment of nano‐CaCO₃ in the presence of PVC and coupling agent.

Molau test results of the samples in THF.     

Swelling and Adsorption Properties of Hydrophobic Poly[(N‐(3‐(dimethylamino)propyl)methacrylamide)‐co‐(lauryl acrylate)] Hydrogels in Aqueous Solutions of Surfactants

Summary: The swelling and adsorption behavior of a series of hydrophobic poly[(N‐(3‐(dimethylamino)propyl)methacrylamide)‐co‐(lauryl acrylate)] [P(DMAPMA‐co‐LA)] hydrogels was studied as a function of temperature in aqueous solutions of the anionic surfactant sodium dodecyl sulfate (SDS) and the cationic surfactant dodecyltrimethylammonium bromide (DTAB). Between 0 and 41.7 mol‐% of lauryl acrylate (LA) were used as a hydrophobic comonomer in the hydrogel synthesis. In SDS solutions, the equilibrium swelling ratio of the hydrogels decreased with increasing temperature. At SDS concentrations below 0.0083 M , the hydrogels exhibited an almost linear swelling behavior. However, for SDS concentrations above 0.0083 M , non‐linear swelling behavior was observed in the range 28–36 °C. In contrast to the SDS solutions, in all DTAB solutions the equilibrium swelling ratio of the hydrogels increased with increasing temperature and a positive temperature sensitive property was shown for all P(DMAPMA‐co‐LA) hydrogels. The adsorption capacities of the hydrogels in aqueous solutions of SDS and DTAB were determined via surface tension measurements. An increase in the LA content in the hydrogel caused an increase in the amount of adsorbed surfactant molecules in both media.

Effect of the DTAB concentration on the adsorption capacities of P(DMAPMA‐co‐LA) hydrogels.     

Novel Poly(N‐isopropylacrylamide)‐graft‐poly(vinylidene fluoride) Copolymers for Temperature‐Sensitive Microfiltration Membranes

In the present work, we report on the synthesis and characterization of poly(vinylidene fluoride) (PVDF) with N‐isopropylacrylamide (NIPAAM) polymer side chains from molecular graft copolymerization in solution. The copolymer can be readily cast into temperature‐sensitive microfiltration (MF) membranes by the phase inversion technique. The copolymer approach to membrane fabrication allows a much better control of the physicochemical nature of the membrane pores through the variation in graft concentration, membrane casting temperature and concentration of the membrane casting solution.

     

Effect of Maleated Compatibilizer on Performance of PLA/Wheat Straw‐Based Green Composites

In this study, the use of PLA‐g‐MA is investigated as a potential method for improving interfacial adhesion between agricultural residues and PLA, with the goal of enhancing mechanical properties. Compatibilization was achieved by using PLA‐g‐MA prepared via reactive extrusion. Green renewable and compatibilized PLA/wheat straw composites were extruded and injection‐molded. Addition of 3 and 5 phr PLA‐g‐MA to the composites resulted in significant improvements in tensile strength (20%) and flexural strength (14%) of the composites, matching that of the neat polymer. The observed improvement in strength was attributed to the good interfacial adhesion between the fiber and matrix.

     

Improvement of Flex‐Fatigue Life of Carbon‐Black‐Filled Styrene‐Butadiene Rubber by Addition of Nanodispersed Clay

Summary: The flex‐fatigue life of carbon‐black‐filled SBR was dramatically improved by incorporation of 4–5 phr nanodispersed clay. Addition of clay did not decrease the degree of crosslinking of the composite but improved the hysteresis and tearing energy. ESEM observation of the flexing‐fracture morphology indicated that nanodispersed clay layers had the advantage over carbon black in that they could blunt the crack.

Effect of the clay amount on the flex fatigue life of the composites.     

Synthesis of Block Copolymers containing Chain‐Controlled Aramid and Fluoroethylene Segments

Summary: Novel block copolymers containing aromatic polyamide (aramid) and fluoroethylene segments were synthesized by a two‐step solution polycondensation. This synthetic method could control the chain‐length of aramid segments and these copolymers could have high structural regularity. The number‐average molecular weight ( ) of one of these polymers is over 2.0 × 10⁴. Incorporating fluoroethylene segments improves the solubility of the resulting polymer compared with conventional aramids.

The synthesis of the fluoroethylene‐aramid block copolymers.     

On the Role of Extensional Flow in Morphology and Property Modifications of MWCNT/Polyamide‐Based Fibers

Unfilled and MWCNT‐filled PA fibers are prepared and the effect of the extensional flow on their mechanical performance and morphological variations is investigated. Morphological analyses using SEM, TEM, and SAXS suggest a stronger orientation of the MWCNTs along the fiber direction with increasing extensional flow. A particular MWCNT bundle formation in the PA drawn nanocomposite fibers is observed for the first time, and a pull‐out of the central nanotube in some bundles is noted. The maintenance of the “shish‐kebab” structure upon extensional flow is responsible for the mechanical improvements and dimensional stability in MWCNT‐filled PA fibers.

     

Matrimid Aerogels by Temperature‐Controlled,Solution‐Based Crosslinking

This paper reports on a temperature‐controlled, solution‐based method to prepare diamine crosslinked Matrimid aerogels. Addition of a diamine to a preheated polymer solution resulted in a well‐dispersed solution, allowing formation of a homogeneous gel upon cooling. The gels (studied by FTIR and AFM) were dried by solvent extraction with supercritical CO₂. The resulting aerogels showed surface areas of approximately 150 m² · g^?1 and porosities of 0.66–0.69 mL · g^?1 with polymer domains and pore sizes of tens of nanometers. A room temperature‐prepared, inhomogeneous aerogel gave approximately 250 m² · g^?1 and 0.31 mL · g^?1 with meso‐ and micropores. SEM images of the aerogels show similar surface features as AFM images of the Matrimid solvent gels.

     

Thermo‐Physical and Impact Properties of Epoxy Containing Epoxidized Linseed Oil, 2

Summary: Biobased neat epoxy materials containing epoxidized linseed oil (ELO) were processed with an amine curing agent. A defined amount of diglycidyl ether of bisphenol F (DGEBF) was replaced by ELO. The thermophysical properties of the amine‐cured biobased neat epoxy were measured by dynamic mechanical analysis (DMA). The Izod impact strength increased with an increase in the amount of ELO added. The change in the Izod impact strength was correlated with the thermophysical properties measured by DMA.

Relation between the Izod impact strength and loss factor for amine‐ and anhydride‐cured ELO‐containing epoxy resins.     

Self‐Assembling of SBS Block Copolymers as Templates for Conductive Silver Nanocomposites

Novel nanocomposites based on conductive Ag nanoparticles and a self‐assembled polystyrene‐block‐polybutadiene‐block‐polystyrene (SBS) block copolymer were investigated. Good confinement of the nanoparticles into polystyrene microphase was achieved by the addition of DT as surfactant. The polymeric matrix kept its hexagonal order packed cylindrical structure up to 7 wt.‐% content of Ag nanoparticles. An electrostatic force microscopy (EFM) analysis of well‐dispersed metal‐organic hybrid Ag/SBS films was used to characterize the electric behavior of the conductive nanocomposites.

     

CNT Based Elastomer‐Hybrid‐Nanocomposites with Promising Mechanical and Electrical Properties

CNT based elastomer‐hybrid‐nanocomposites prepared by melt mixing have been investigated showing promising results in technologically relevant electrical, mechanical, and fracture‐mechanical properties. It is demonstrated that the incorporation of CNT in silica‐filled natural rubber results in a good dispersion of the CNT. The materials show an enhanced mechanical stiffness and tensile strength, an increased modulus, and a high electrical conductivity with quite low amounts of CNT, though the tear resistance under dynamical loading is slightly reduced. Using DMA and dielectric spectra, a better understanding of the conduction mechanism, the polymer/tube interaction, and the filler networking in CNT nanocomposites is achieved.

     

Poly[(vinylidene fluoride)‐co‐trifluoroethylene] Membranes Obtained by Isothermal Crystallization from Solution

Electroactive macroporous poly[(vinylidene fluoride)‐co‐trifluoroethylene] membranes have been produced by solvent evaporation at room temperature, starting with a diluted solution of the copolymer in dimethylformamide. The pore architecture consists of interconnected spherical pores. This architecture is independent of the membrane thickness. The thickness of the membranes ranges from a few to several hundred µm, using spin coating and evaporation in static conditions, respectively. The pore structure is explained by a spinodal decomposition of the liquid/liquid phase separation and crystallization in the copolymer‐rich phase.

     

Laccases to Improve the Whiteness in a Conventional Bleaching of Cotton

This study reports for the first time on the enhancement of the bleaching effect achieved on cotton using laccase enzyme. Laccases applied in short‐time batchwise or pad‐dry processes prior to conventional peroxide bleaching, improved the end fabric whiteness. The whiteness level reached in the combined enzymatic/peroxide process was comparable to the whiteness in two consecutive peroxide bleaches.

Effect of 10 min laccase pre‐treatment at 60 °C, pH 5 on fabrics whiteness before and after a conventional hydrogen peroxide bleaching.     

Monomers for Adhesive Polymers 12 Synthesis and Free‐Radical Homo‐ and Copolymerization of 2‐Ethoxycarbonylallyl 5‐(1,2‐dithiolane‐3‐yl)‐pentanoate

The 2‐ethoxycarbonylallyl 5‐(1,2‐dithiolane‐3‐yl)‐pentanoate monomer (AODS) includes in its molecular structure C?C and S? S reactive bonds allowing it to behave as a bi‐functional monomer, possessing two groups, however, with different reactivity for use in polymer chain building. The polymerization‐specific features of this monomer are the absence of auto‐acceleration and polymer chain crosslinking. Polymerization proceeds readily through most free‐radical initiators. One exception, carboxy‐peroxides are rapidly decomposed without the production of free radicals. AODS is partially converted to a gel without the consumption of double bonds during monomer dissolution in certain organic solvents and after being mixed in solution with carboxy‐peroxides. The determined AODS‐co‐MMA copolymerization parameters are r₁ = 2.61, r₂ = 0.23 if Luperco peroxide is used as a polymerization initiator, and r₁ = 2.71, r₂ = 0.38 if AIBN is used.

     

Elaboration of Poly(ε‐caprolactone)‐g‐TiNbO5 Nanocomposites via in situ Metal Complex Initiated Intercalative Polymerization

Summary: The preparation of poly(ε‐caprolactone)‐g‐TiNbO₅ nanocomposites via in situ intercalative polymerization of ε‐caprolactone initiated by an aluminium complex is described. These nanocomposites were obtained in the presence of HTiNbO₅ mineral pre‐treated by AlMe₃, but non‐modified by tetraalkylammonium cations. These hybrid materials obtained have been characterized by Fourier transform infrared absorption spectroscopy, wide‐angle X‐ray scattering, scanning electron microscopy, and dynamic mechanical analysis. Layered structure delamination and homogeneous distribution of mineral lamellae in the poly(ε‐caprolactone) (PCL) is figured out and strong improvement of the mechanical properties achieved. The storage modulus of the nanocomposites is enhanced as compared to pure PCL and increases monotonously with the amount of the filler in the range 3 to 10 wt.‐%.

SEM image of the fractured surface of a PCL‐TiNbO₅ nanocomposite film.     

A Novel N‐Succinylchitosan‐graft‐Polyacrylamide/Attapulgite Composite Hydrogel Prepared through Inverse Suspension Polymerization

A novel N‐succinylchitosan‐graft‐polyacrylamide/attapulgite composite hydrogel was prepared by using N‐succinylchitosan, acrylamide and attapulgite through inverse suspension polymerization. The result from FTIR spectra showed that ? OH of attapulgite, ? OH and ? NHCO of N‐succinylchitosan participated in graft polymerization with acrylamide. The introduced attapulgite could enhance thermal stability of the hydrogel. Scanning electron microscopy observation indicates that the composite hydrogel has a microporous surface. The volume ratio of heptane to water, weight ratio of acrylamide to N‐succinylchitosan and attapulgite content have great influence on swelling ability of the composite hydrogel. The composite hydrogel shows higher swelling rate and pH‐sensitivity compared to that of without attapulgite.