Synthesis and characterization of vinyl silane modified imidazole copolymer as a novel corrosion inhibitor

For a novel corrosion inhibitor for copper, the free radical copolymerization of vinyl imidazole (VI) and vinyl trimethoxy silane (VTS) was carried out in benzene at 68 °C using azobisisobutyronitrile (AIBN) as an initiator. The reactivity ratios of the two monomers were determined from instantaneous composition diagram: r _VI = 3.22 and r _VTS = 0. Thermal stability of poly(VI-co-VTS) depended on VTS mole fraction in the feed rather than the molecular weight of the copolymer, due to the disiloxane bond linkages formed during heating. Received: 21 October 1996/Revised: 9 December 1996/Accepted: 12 December 1996     

Application of a mathematical model to the study of the glass transition temperature in polymer electrolyte precursor systems

To the purpose of studying the effect of composition on the glass transition temperature (Tg) of a series of polymer electrolytes based on blends of polyethylene oxide (PEO), poly(octafluoropentoxytrifluoroethoxy)phosphazene (PPz) and poly(epichlorhydrine), a mathematical model was applied to results obtained through DSC determination using seven ternary blends selected by an experimental design. The parameters of the model were chosen by means of stepwise linear regression method. The final model proved to be appropriate (R² = 0.997; s = 0.99 K) to predict the Tg values. From a structural point of view it was found that the lowest Tg values were obtained for the blends containing the smallest PECH portion. Received: 18 November 1996/Revised: 2 December 1996/Accepted: 3 December 1996     

Synthesis and polymerization of 3-(t-butoxycarbonyl)-1-vinylcaprolactam and application as deep UV resists

Poly(3-(t-butoxycarbonyl)-1-vinylcaprolactam) (PBCVC) was synthesized and evaluated as a potential deep UV photoresist. The synthesized polymer has excellent transmittance at 248 nm (absorbance = 0.018 μm⁻¹). In addition, PBCVC possesses good thermal stability up to 220 °C and a high glass transition temperature (174 ∼ 190 °C). The thermal deprotection of side chain ester groups of PBCVC occurs at 220 °C, whereas in the presence of acid the cleavage of the t-butyl ester groups of PBCVC begins at about 80 °C, and followed by evolution of carbon dioxide at about 150 °C. Deprotection of PBCVC gave the corresponding polymer, poly(1-vinylcaprolactam-3-carboxylic acid). The contrast of the PBCVC resist system was not deteriorated with the post-exposure delay (PED) time. Received: 2 September 1996/Revised: 18 December 1996/Accepted: 20 December 1996     

Radical polymerization of (trimethylsilylethynyl)styrene and thermal properties of polystyrene with ethynyl group

The radical polymerizations of 2-, 3-, and 4-(trimethylsilylethynyl)styrenes (1 a – c) and copolymerizations of 1 a – c (M₁) with styrene (M₂) have been studied. Copolymerization parameters were determined as r₁ = 1.22 and r₂ = 0.54 for 1 a, ₁ = 1.10 and r₂ = 0.90 for 1 b, and r₁ = 1.42 and r₂ = 0.38 for 1 c. The deprotection of the trimethylsilyl groups in poly[(trimethylsilylethynyl)styrene] (2 a – c) and poly[(trimethylsilylethynyl)styrene-co-styrene] (4 a – c) using (C₄H₉)₄NF smoothly proceeded to yield poly(ethynylstyrene) (3 a – c) and poly(ethynylstyrene-co-styrene) (5 a – c), respectively, which underwent curing reactions at elevated temperature to form crosslinking polystyrenes. Received: 31 March 1997/Revised: 2 June 1997/Accepted: 3 June 1997     

Dynamic mechanical behaviour of random copolymers of a LC-methacrylate and octyl methacrylate

The dynamic mechanical behaviour of random copolymers of LC monomer-1-(hexyloxycarbonyl)ethyl 4-[4-(methacryloyloxy)benzoyloxy]benzoate (HB) and octyl methacrylate (OMA) was studied in the main transition and flow regions. Even though the aliphatic end groups of the side chain of HB and OMA are roughly the same, the T _g temperature of poly(HB) is ∼ 80 K higher than that of poly(OMA); this fact is due to the presence of the stiff phenyl benzoate mesogenic group in the side chain of HB. With increasing content of OMA in the copolymer the superimposed curves of the storage G′ _p and loss G′′ _p moduli at a constant temperature shift towards shorter frequencies. It has been shown that this shift is mainly due to an increase of the free volume in the copolymers with increasing content of OMA. While HB monomer shows liquid crystalline (LC) properties, its polymer (poly(HB)) and random copolymers with OMA show only isotropic thermal behaviour because no flexible spacer is present in the side chain of HB which would decouple the main chain and mesogenic group motions. This means that neither the homopolymer of HB, nor its copolymers with a flexible comonomer retain the LC properties of the starting LC monomer, HB. Received: 26 September 1996/Revised: 7 November 1996/Accepted: 7 November 1996     

Synthesis and thermal properties of fullerene-containing polymethacrylates

Three poly(methyl methacrylate-co-2-bromoethyl methacrylate) samples were prepared. The bromine groups in the copolymers were converted to azide groups followed by reaction with fullerene (C₆₀) to afford fullerene-containing polymethacrylates. The glass transition temperatures (T_gs) and heat capacity changes (ΔC_p) at T_g of these polymers were measured by differential scanning calorimetry. With increasing fullerene content in the polymethacrylate, the T_g value increases while the ΔC_p value decreases. The incorporation of fullerene improves the thermal stability of the polymethacrylate as shown by thermogravimetric analysis. Received: 25 February 1997/Revised: 12 May 1997/Accepted: 13 May 1997     

Effects of phenyl-based pendent groups on helical conformation of poly(<Emphasis Type="Italic">N</Emphasis>-propargylamides)

Five achiral N-propargylamide monomers with various phenyl-based substitutents, [HC ≡ CCH₂NHCOR, R for M1: C₆H₄CH₃; M2: C₆H₄CH₂CH₃; M3: C₆H₄(CH₂)₂CH₃; M4: C₆H₄(CH₂)₃CH₃; M5: C₆H₄C(CH₃)₃], were synthesized and polymerized with a rhodium catalyst, (nbd)Rh⁺B^-(C₆H₅)₄ (nbd = 2,5-norbornadiene). The corresponding five homopolymers were obtained in high yields of 90–95% and with moderate molecular weights (M _n ≥ 10 000). All the polymers possessed high cis contents (≥95%). Poly(1)–poly(3) exhibited UV-vis absorption peaks at approx. 350 nm, which indicates that the three polymers formed helical conformations, while no UV-vis absorption peaks could be observed in poly(4) and poly(5) in the wavelength range of 320–500 nm, demonstrating that these two polymers could not adopt helical structures under the examined conditions. To confirm the helical structures formed in poly(1)–poly(3), a chiral monomer, M6, was utilized to copolymerize with M2, which was used as the representative for M1−M3. M6 was utilized since its polymer could form stable helices under suited conditions. The resulting copolymers exhibited remarkable CD effects, however, the maximum wavelength in the copolymers varied remarkably, mainly depending on the composition of the copolymers. It is concluded that in the formation of ordered helical conformations, the substitutents of varied bulk led to different steric repulsion and varied synergic effects among the neighboring pendent groups.     

Compatibilization of low-density polyethylene/polystyrene blends by segmented EB(PS-block-EB) n block copolymers

Hydrogenated segmented poly[butadiene-block-(styrene-block-butadiene)_n] block copolymers, which were developed by use of a polymeric iniferter technique, were tested on their compatibilizing effectiveness for (10/90) LDPE/PS blends. They were found to be effective compatibilizers for this mixture, already giving a pronounced improvement in both tensile strength and strain of the blend at block copolymer concentrations of one percent. A concentration of five weight percent of segmented block copolymer provided a tenfold improvement in blend toughness. The effectiveness of the segmented block copolymers was found be dependent on the block copolymer composition. Block copolymer compositions of close to 50 : 50 EB : PS gave the best results. Received: 23 September 1996/Revised: 4 November 1996/Accepted: 7 November 1996     

Separation of block copolymers from parent homopolymers by means of liquid chromatography at the critical adsorption point

The characterization of a block copolymer consisting of blocks of tetrahydrofuran, THF, and methyl methacrylate, MMA, was attempted with the aid of liquid chromatography, LC, at the critical adsorption point, CAP. The conditions applying to the CAP at 30 °C for the homopolymers are: PTHF: eluent composition: THF : acetonitrile = 50 : 50, w/w; column: Nucleosil C₁₈. PMMA: eluent composition: THF : n-hexane = 81.8 : 18.2, w/w; column: bare silica gel. The presence of homo PTHF and of homo PMMA in the crude block copolymer was evidenced. Moreover, chromatography at the CAP for PMMA showed that the block copolymer contains multiblock (triblock) fractions. The formation of triblock copolymer is expected when the polymerization of MMA is terminated (partially) by combination. In conclusion, LC at the CAP is a powerful tool to characterize block copolymers regarding the presence of homopolymer and multiblock (triblock) fractions. Received: 13 February 1997/Revised: 18 March 1997/Accepted: 24 March 1997     

Phase behaviour of poly(benzophenoneimide)s having n-alkyloxymethyl side chains

A series of poly(benzophenoneimide)s (C_m-BP-PIs) having n-alkyloxymethyl side chains (−CH₂O-n-CmH_2m+1, m = 4, 6, 8) have been examined by X-ray diffraction, differential scanning calorimetry (DSC) and polarizing optical microscopy. The samples showed basically two phase transitions and both transition temperatures decreased with increasing side chain length. The first transitions were ascribed to glass transitions and the second ones were assigned to liquid crystal-to-isotropic transitions. Eicosane (n-C₂₀H₄₂) which is chemically very similar to the side chain was miscible with the side chains of C₈-BP-PI, which induced depression of the glass transition temperature. Received: 17 February 1997/Revised: 1 April 1997/Accepted: 4 April 1997     

Synthesis and free radical polymerization of 4-{1′-(2″-methacryloyloxyethoxy)-5′-naphthyliminomethylidene}-4′-nitrostilbene for nonlinear optical applications

4-{1′-(2″-Methacryloyloxyethoxy)-5′-naphthyliminomethylidene}-4′-nitro-stilbene 6 was prepared by the reactions of methacryloyl chloride with 4-{1′-(2″-hydroxyethoxy)-5′-naphthyliminomethylidene}-4′-nitrostilbene 5. Compound 5 was synthesized from 4′-methyl-4-nitrostilbene by several reaction steps. Monomer 6 was polymerized with DTBP as a radical initiator to obtain polymer with 4-(1′-oxy-5′-naphthyliminomethylidene)-4′-nitrostilbene, which is presumably effective chromophore for second-order nonlinear optical applications in the side chain. The resulting polymethacrylate 7 showed a thermal stability up to 300 °C in TGA thermogram, and the T_g value obtained from DSC thermogram was 120 °C, which is acceptable for NLO device applications. Received: 14 October 1996/Accepted: 11 December 1996     

Relaxation patterns of endlinking polydimethylsiloxane near the gel point

While the rheological behavior at the gel point (GP) itself is well known, many questions remain about the approach to the gel point (from either side). For studying this phenomenon, rheological experiments were performed on crosslinked polydimethylsiloxanes (PDMS) and characteristic patterns in the relaxation behavior were abstracted into a phenomenological model for the relaxation time spectrum. The well known power law with slope-n and cutoff at the longest relaxation time λ _max governs the relaxation near the gel point. Beyond the gel point, an additional box-like contribution appears in the spectrum. The relaxation exponent n decreases with increasing extent of crosslinking. The longest relaxation time λ _max and equilibrium modulus G_e show power-law scaling with the distance from the gel point, |p − p_c|. For samples with imbalanced stoichiometric ratios r ≥ 1, the function n (p − p_c) is independent of r. Samples with strong crosslinker deficiency (r = 0.5) exhibit a different functional form for n (p − p_c) from those with r ≥ 1. The power law relaxation with decreasing n in the terminal zone was found previously for a different crosslinking system. It seems to be a common pattern for partially crosslinked materials from polymeric precursors. Received: 11 December 1997/Revised version: 18 December 1997/Accepted: 18 December 1997     

Effect of the crosslinking with 1,1,1-trimethylolpropane trimethacrylate on 5-fluorouracil release from poly(2-hydroxyethyl methacrylate) hydrogels

The aim of this study is to examine the influence of crosslinking density on 5-Fluorouracil release from poly(2-hydroxyethyl methacrylate) (PHEMA) hydrogels crosslinked with 1,1,1-trimethylolpropane trimethacrylate (TPT). PHEMA hydrogels were synthesized by bulk polymerization with different proportions of TPT (1 – 10 wt%) as crosslinker agent and ammonium persulphate as initiator, enabling polymerization in the feed mixture in the presence of water. As a result, 5-FU could be trapped by including it as a sodium salt in the feed mixture of polymerization. Discs with 5-FU loads between 1 – 16 mg/disc were obtained. Swelling and 5-FU release kinetics studies were carried out in saline solution at 310 K. The diffusion studies were in accordance with Fick's second law during the initial stages, enabling the diffusion coefficients of the process to be determined. The time required for discs to reach total 5-FU release was between 35 h and 160 h and was a function of crosslinking density of the gels and 5-FU load of the discs. Received: 12 July 1996/Revised version: 8 October 1996/Accepted: 15 October 1996     

Syndiotactic polymerization of methyl methacrylate with Ni(acac)<Subscript>2</Subscript>-methylaluminoxane catalyst

In this study, syndiotactic-rich poly(methyl methacrylate) (PMMA) is obtained by using a soluble nickle acetylacetonate [Ni(acac)₂] and modified methylaluminoxane (MMAO-3A) catalyst system under modest polymerization conditions. The main purpose of this work is concerned with the study of previous conflicting stereospecificity data. Types of MAO, temperature of polymerization, MAO/Ni(acac)₂ (Al/Ni) mole ratio, and various solvents have been investigated in the MMA polymerization. Particularly, high syndiotactic PMMA [(rr) > 91 %] has been obtained when MMAO-3A is used as cocatalyst with Al/Ni ratio of ca. 50 or polymerization temperature ca. 0 °C. As expected, the prepared syndiotacticity-rich PMMA has a higher glass transition temperature (T _g) within 120 ~ 127 °C. The details of the polymerization mechanism, especially in relation to the stereoregularity problems are under investigation.     

Syntheses and radical ring-opening polymerizations of 1,1-bis(hydroxymethyl)-2-vinylcyclopropane and 1,1-bis(methoxymethyl)-2-vinylcyclopropane

Homo- and copolymerizations of 1,5-hexadiene with ethene and styrene using halfsandwich metallocene catalyst Me₂Si(Me₄Cp)(N-tert.-butyl)TiCl₂/MAO (Cp = cyclopentadienyl, Me = methyl, MAO = methylalumoxane) were investigated. According to ¹³C-NMR spectroscopic microstructure analysis, cyclopolymerization of 1,5-hexadiene afforded randomly distributed cis- and trans-cyclopentane rings in the homo- and copolymer backbone. 1,5-hexadiene incorporation reached 52 mol-%. The ratio of vinyl side chains to cyclopentane rings was controlled by 1,5-hexadiene concentration, where low 1,5-hexadiene concentration promoted cyclopolymerization. Copolymer glass transition temperatures increased with increasing content of cyclic units in the backbone. Styrene was used successfully as termonomer in ethene/1,5-hexadiene polymerization, resulting in a semicrystalline terpolymer with cyclic and styrenic units in the polymer backbone. Received: 5 September 1996/Accepted: 11 November 1996     

Relationships between lateral force and viscoelastic properties for amorphous polymer films based on lateral force microscopy

Summary. The relationships between lateral force and viscoelastic properties of amorphous polymer surfaces with Tg's lower and higher than room temperature (295 K, RT) and their blend systems have been studied on the basis of lateral force microscopic (LFM) measurement. Under the conditions of scanning rate of 10²–10⁵ nm sec^-1, normal load of 5 nN and RT, the lateral forces of poly(methyl methacrylate) (PMMA) and polyisoprene (PI) homopolymers with Tg's fairly higher and lower than RT, respectively, did not depend on the scanning rate. Whereas, the lateral force of poly(methyl acrylate) (PMA) with Tg ≤ RT decreased with an increase in the scanning rate. Also, poly(vinyl acetate) (PVAc) with Tg ≥ RT showed slight dependence on the scanning rate. The scanning rate dependence of lateral force was similar to the frequency dependence of mechanical loss modulus. The results indicate that the magnitude of lateral force strongly depends on the state of thermal molecular motion. The lateral force-viscoelastic properties of miscible polymer blends was also investigated by LFM. Received: 30 June 1997/Revised: 24 July 1997/Accepted: 29 July 1997     

The soluble and insoluble product of diphenylzinc-water systems as initiator in styrene polymerization

The solution resulting from reaction between Ph₂Zn and H₂O in benzene was used by itself and separated in soluble and insoluble fractions to initiate styrene polymerization. The soluble fraction produced the largest polymer conversion while the insoluble was reponsible of the highest molecular weights. Resulting polystyrenes were atactic but up to 80 – 85% syndiotactic triads were detected by ¹H-NMR analysis. Polystyrene obtained using benzene as solvent showed a low crystalline content while the polymer obtained using dichloromethane did not produce any crystalline fraction. Received: 10 December 1996/Revised: 15 April 1997/Accepted: 18 April 1997     

Synthesis of amphiphilic triarm star block copolymers

We describe the synthesis and the characterization of amphiphilic triarm star block copolymers based on polystyrene, poly(methyl methacrylate), poly(ε caprolactone), poly(l lactide) and poly(ethylene oxide) blocks. This synthesis has been achieved by a new route consisting in 2 successive initiation steps on a core molecule (a 1,1-diphenyl-ethylene derivative bearing a protected hydroxy function) located at the end of a first block. Some results on adsorption onto TiO₂ and micellization studies are given. Preliminary results on solid state indicate an increase of the miscibility of the different incompatible blocks. Received: 3 November 1997/Revised version: 1 December 1997/Accepted: 2 December 1997     

Temperature dependent electrical conductivity of p-doped poly(3,4-ethylenedioxythiophene) and poly(3-alkylthiophene)s

Summary Temperature dependent electrical conductivity of substituted polythiophenes (poly(3,4-ethylenedioxythiophene) PEDOTh and head-to-tail type poly(3-alkylthiophene) HT-P3RTh) has been measured. The electrical conductivity (σ) of p-doped PEDOTh and HT-P3RTh obeys equations of a type, ln σ= ln σ_o− (T_o/T)^0.25, with the T_o value of about 10⁵–10⁷ K. Received: 21 December 1998/Revised version: 8 February 1999/Accepted: 15 February 1999     

Synthesis and regular reflection property of cocoon-like poly(methyl methacrylate) particles by seeded suspension polymerization

Synthesis and optical properties of cocoon-like poly(methyl methacrylate) (CPM) particles in the size range of D _n  = 3.0–6.5 μm were studied. The synthesis of these anisotropic particles consists of two steps. The spherical poly(methyl methacrylate) (PMA) particles (D _n  = 2.2–5.5 μm) cross-linked by 0.2–0.8 wt% ethylene glycol dimethacrylate (EGDMA) were prepared by dispersion polymerization, using a combination of poly(vinyl pyrrolidone) (PVP) and sodium di-(2-ethylhexyl) sulfosuccinate (NaEHS) as a stabilizer in 94:840 water–methanol. Then, a suspension polymerization of 9:1 methyl methacrylate (MMA)/EGDMA in the presence of the PMA particles as seed at 85 °C in water gave non-spherical, cocoon-like CPM particles, depending on the cross-linking densities of PMA particles. The cocoon-like CPM particles (D _n,c  = 4.0 μm) showed the characteristic features of regular reflection, which can not be attained for conventional poly(methyl methacrylate) particles with a spherical shape. The effects of seed PMA particles with different properties on the formation of cocoon-like CPM particles and their regular reflection properties are described.