In this study, tetra isopropyl ortho titanate (TTIP) and polycaprolactone (PCL) were chosen as the ce- ramic precursor and the continuous phase, respectively, for the preparation of novel nanocomposites by using an in situ sol-gel process. In addition, acrylic acid grafted polycapro- lactone (PCL-g-AA) was investigated as an alternative to PCL. The hybrids (PCL/TiO2 and PCL-g-AA/TiO2) were characterized via Fourier transform infrared (FTIR) spectros- copy, dynamic mechanical thermal analysis (DMA), X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetry analysis (TGA), and Instron mechanical testing. It was found that the carboxylic acid groups of acrylic acid acted as coordination sites for the titania phase to form chemical bonds, thus improving the properties of the acrylic acid grafted composite compared with its acrylic- acid-free counterpart. The TiO2 content also determined the strength of interfacial bonding between the polymer chains and the ceramic phase, as shown by changes in glass tran- sition temperature (Tg) with TiO2 content. The maximum values of tensile strength and Tg were obtained with the PCL-g-AA/TiO2 composite at 10 wt % TiO2 .A t TiO 2 con- tents above this, excess particles led to segregation between the organic and inorganic phases. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1749 -1757, 2004

In situ polymerization of titanium isopropoxide in polycaprolactone: Properties and characterization of the hybrid nanocomposites

In this article, the properties of a polycapro- lactone and starch composite (PCL/starch) and an acrylic acid grafted polycaprolactone and starch composite (PCL-g- AA/starch) were examined by Fourier transform infrared spectroscopy, nuclear magnetic resonance, differential scan- ning calorimetry, Instron mechanical testing, and scanning electron microscopy. Mechanical properties of PCL became significantly worse when it was blended with starch, due to the poor compatibility between the two phases. Much better dispersion and homogeneity of starch in the polymer matrix was obtained when PCL-g-AA was used in place of PCL in the composite. Improved mechanical and thermal properties of the PCL-g-AA/starch composite, notably an increase in tensile strength at breakpoint, evidenced its superiority to the PCL/starch one. Furthermore, PCL-g-AA/starch was more easily processed than PCL/starch because the former had lower melt viscosity. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2888 -2895, 2003

Performance of an acrylic acid grafted polycaprolactone/starch composite: Characterization and mechanical properties

The accurate characterization of molar-mass distributions of poly(acrylic acid) (PAA) and poly(methacrylic acid) (PMAA) by size-exclusion chromatography (SEC) is addressed. Two methods are employed: direct aqueous-phase SEC on P(M)AA and THF-based SEC after esterification of P(M)AA to the associated methyl esters, P(M)MA. P(M)AA calibration standards, P(M)AA samples prepared by pulsed-laser polymerization (PLP), and PAA samples prepared by reversible addition-fragmentation chain transfer (RAFT) are characterized in a joint initiative of seven laboratories, with satisfactory agreement achieved between the institutions. Both SEC methods provide reliable results for PMAA. In the case of PAA, close agreement between the two SEC methods is only observed for samples prepared by RAFT polymerization with weight-average molar mass between 80 000 and 145 000 g mol−1 and for standards with peak molar masses below 20 000 g mol−1. For standards with higher molar masses and for PLP-prepared PAA, the values from THF-based SEC are as much as 40% below the molar masses determined by aqueous-phase SEC. This discrepancy may be due to branching or degradation of branched PAA during methylation. While both SEC methods can be recommended for PMAA, aqueous-phase SEC should be used for molar-mass analysis of PAA unless the sample is not branched.

SEC Analysis of Poly(Acrylic Acid) and Poly(Methacrylic Acid)

The aim of this work is the production of new nanocomposites from metallocene polyethylene-octene elastomer (POE), montmorillonite and biodegradable starch by means of a melt blending method. Characterizations of clay, modified clay, POE, POE-g-AA, and the hybrids produced from polymer, clay, and/or starch were performed by X-ray diffraction (XRD) spectroscopy, Fourier transform infrared (FTIR) spectrophotometer, differential scanning calorimetry (DSC), thermogravimetry analyzer (TGA), scanning electron microscope (SEM), and Instron mechanical tester. As to the results, organophilic clay can be well dispersed into acrylic acid grafted polyethylene-octene elastomer (POE-g-AA) in nanoscale sizes since cetyl pyridium chloride is partially compatible with POE-g-AA and allows POE-g-AA chains to intercalate into clay layers. Based on consideration of thermal and mechanical properties, it is also found that 12 wt % of clay content is optimal for preparation of POE-g-AA/clay nanocomposites. The new partly biodegradable POE-g-AA/clay/starch hybrid could obviously improve the elongation and the tensile strength at break of the POE-g-AA/starch hybrid since the former can give the smaller starch phase size and nanoscale dispersion of silicate layers in the polymer matrix. The nanocomposites produced from our laboratory can provide a stable tensile strength at break when the starch content is up to 40 wt %. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 397–404, 2005

Synthesis and characterization of polyethylene-octene elastomer/clay/biodegradable starch nanocomposites

In this study, grafting of acrylic acid (AA) onto metallocene-based polyethylene-octene elastomer (POE) was investigated by using benzoyl peroxide as an initiator. Grafted product was characterized by using Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, X-ray diffraction spectroscopy, and differential scanning calorimetry (DSC). Both the grafting percentage and the gel yield, at equilibrium, were higher for POE containing lower degree of comonomer content. In all cases, the crosslinking reaction was accompanied by the predominant graft reaction due to the competition of POE macroradical and excited AA. From the result of DSC and X-ray characterizations, it was found that the change of crystallinity is slight when the gel is removed from POE-g-AA copolymers. It was also proven that the effect of gel formation on the properties of the copolymer could be neglected because of the low gel yield. So, the graft method proposed in this article can produce low gel yield copolymer. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2905–2912, 2002

Graft reaction of acrylic acid onto metallocene-based polyethylene-octene elastomer

To synthesize a novel gel capsule containing a hydrophobic shell and hydrophilic core portions, we investigated the esterification of poly(acrylic acid) gel-1,8-diazabicyclo[5,4,0]undec-7-ene salt (DAA) with alkyl bromides. The esterification of DAA with benzyl bromide proceeded almost quantitatively in N-methyl-2-pyrrolidone (NMP) from the surface, although small amounts of carboxylic acids were produced as side products. The reaction gave a new gel capsule consisting of a hydrophilic unreacted core and hydrophobioc esterified shell, and finally afforded poly(benzyl acrylate) gel. Reactions of DAA with alkyl bromides were carried out under various conditions, and analyzed kinetically. The observed reaction rate markedly affected the molecular size of the alkyl halides and solvents rather than reactivity of their combinations. This suggests that the overall reaction depends markedly on diffusion rate of alkyl bromides and solvents through the reacted shell layer. The thickness of the shell layer was easily controlled by reaction conditions. The swelling of the gel capsule and release of Rose-Bengal from the gel capsule were studied. The results suggested that the structure of the shell layer controls properties such as the swelling rate, burst time, and releasing rate of chemicals.

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Novel Synthesis of Gel Capsule by Esterification of Poly(acrylic acid) Gel

To synthesize a novel gel capsule containing a thermo-sensitive shell and hydrophilic core portions, we investigated the amidation of poly(acrylic acid) (AA) gel–1,8-diazabicyclo[5,4,0]undec-7-ene salt (DAA) with isopropylamine (IPA). The reaction of DAA with IPA proceeded almost quantitatively in NMP in the presence of triphenylphosphine (TPP). However, the amidation took place in competition with the esterification to give a copolymer of N-isopropylacrylamide with phenyl acrylate. The selectivity of amidation increased with increasing the IPA concentration although the observed decreasing rate of unswollen part was independent of the concentration. When the reaction was carried out at 1.0 mol L-1 of the IPA concentration in NMP, the amidation from the outside took place almost selectively to give poly(N-isopropylacrylamide) gel through a DAA-NIPA type gel capsule consisting of a hydrophilic unreacted core part and amidated shell layer. The swelling of the gel capsule and release of Methyl Orange from the gel capsule were studied. Above the lower critical solution temperature (LCST) of poly(N-isopropylacrylamide) gel, the gel capsule swelled as well as DAA, and the shell layer did not work as a permeability barrier of water. However, an AA-NIPA type gel capsule containing a AA core part and thermo-sensitive shell layer, which was prepared from the neutralization of DAA-NIPA type gel capsule, showed on-off chemical release in response to stepwise temperature changes cross the LCST.

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Synthesis of Poly(N-isopropylacrylamide) Gel and Core-Shell Type Gel with Thermo-Sensitive Shell Layer by Amidation of Poly(acrylic acid) Gel.

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Novel Synthesis of Amphiphilic Core-Shell Type Gel

Polymers having pendant norbornadiene (NBD) moieties and rigid main chains were prepared from reactions in DMF of pendant bromomethyl groups present in polyimides with a potassium carboxylate or phenolate derivatives of NBD using a phase transfer catalyst The substitution was quantitative using tetrabutylammonium bromide at room temperature The photochemical valence isomerization of pendant NBD to quadricyclane (QC) moieties occurred in films upon irradiation with 365 nm light NBD polyimide (P-1a) prepared from hex afluoroisopropylidene-2-bis(phthalic anhydride) and 2,2-bis(3-amino-4-methylphenyl)hexafluoropropane showed a higher photochemical reactivity than the other NBD polyimides when the polymers were irradiated with 365 nm light While usual polyimides have absorptions around 365 nm that hinder the photo-isomerization of NBD and also cause the polymer to decompose because of the irradiation, the P-1a matrix has no absorption at wavelengths above 340 nm and irradiation hardly affected the rate of isomerization When the irradiated NBD polymers were heated, the reversion isomerization of the QC moieties to the original NBD moieties occurred easily concurrent with their decomposition The rigid polyimide structure stabilizes the QC moieties and protects them from degradation during cyclic isomerization between NBD and QC For example, the half-life of a pendant QC moiety in a polyimide is estimated to be 6 years at 25°C

Synthesis of rigid polyimides containing pendant norbornadiene moieties and their valence isomerization between norbornadiene and quadricyclane

Novel Synthesis of Gel Capsule by Thermal Acid-Catalyzed Deesterification of Poly( t -butyl methacrylate) Gel

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Fumihiko Matsuda

Papers

Novel Synthesis of Gel Capsule by Esterification of Poly(acrylic acid) Gel

Synthesis of Poly(N-isopropylacrylamide) Gel and Core-Shell Type Gel with Thermo-Sensitive Shell Layer by Amidation of Poly(acrylic acid) Gel.

Novel Synthesis of Amphiphilic Core-Shell Type Gel

Synthesis of rigid polyimides containing pendant norbornadiene moieties and their valence isomerization between norbornadiene and quadricyclane

Novel synthesis of gel capsule by thermal acid-catalyzed deesterification of poly(t-butyl methacrylate) gel