Journal of Polymer Science Part A: Polymer Chemistry

Polyolefins represented by polyethylene (PE) and polypropylene (PP) are indispensable materials in our daily lives. Our discovery of MgCl₂-supported TiCl₄ catalysts brought about more than 100 times higher activities and extremely high stereospecificities than TiCl₃ catalysts established by Ziegler and Natta, enabling us to simplify and enlarge the commercial production processes of polyolefins, which means the process innovation. Furthermore, they narrowed the molecular weight and composition distributions of PE and PP, enabling us to control the polymer structures precisely and create new products as product innovations. The typical example of the product innovations by the combination of the high stereospecificity and the narrowed composition distribution is high-performance impact copolymer used for an automobile bumper that used to be made of metal. These process and product innovations established these polyolefin industries, which have grown to more than 80 million tons per year of commercial production.

Aluminas were used as support for Cp₂ZrCl₂ and evaluated in ethylene polymerization. Two calcination temperatures were employed, and the metallocene was fixed either directly or after support pretreatment with MAO, TMA, or NaOH. The supported catalysts showed activities comparable to the homogeneous. The support textural properties strongly influenced the catalyst performance. Direct fixation produced catalysts presenting lower activities. Chemical pretreatment of hydrated alumina with TMA originated catalysts whose activities were superior to those obtained by pretreatment with MAO. Pretreatment with NaOH produced the most active catalyst. MW of PE produced by the supported catalysts was higher than with the homogeneous.

ATRP catalysts immobilized on solids generally have reduced control of the polymerizations due to the heterogeneous nature. Here, a reversible catalyst immobilization via hydrogen bonding-mediated self-assembly was demonstrated for the atom transfer radical polymerization (ATRP) of MMA. At elevated temperature, the hydrogen bonds broke and released the catalyst for effective catalysis, but at room temperature, the hydrogen bonds formed, and the catalyst assembled on the solid support for recycling and reuse. The polymers produced by this reversibly supported catalyst had well-controlled molecular weights and low polydispersity similar to those by unsupported catalysts.

Anionic polymerization of MMA in the presence of the divalent transition metal halide (MX₂ = FeBr₂, MnCl₂, CoCl₂, NiBr₂) was investigated. Initiating systems with various combinations of MX₂, lithium diphenylamide (Ph₂NLi), and organolithium (RLi; R = nBu, Me) were effective in producing a high yield of PMMAs at −78 °C in toluene. The tacticity of the resulting PMMAs was highly dependent on the combination of the reagents used for the generation of the initiating systems within a syndiotactic (rr = 59%) to isotactic (mm = 65% range).

Ethylene polymerization by intercalated montmorillonite (MMT) with metallocene and the variation of aggregation morphology of resulting polymer during polymerization was studied by X-ray difraction (XRD), differential scanning calorimetry (DSC) and gel permeation chromatography (GPC). The polymerization kinetics and resulting polymer before and after the silicate registry was destroyed were different. The laminated structure of silicate lowers all-reaction rates, such as propagation, chain transfer and termination reactions, which produces polymer with high molecular weight. Moreover, the melting point of the polymer gradually increased during the in situ polymerization, which indicated that the nanoscopic confinement between solid surfaces affects the crystallization behavior of polyethylene via in situ polymerization.

A convenient calculation for distributions of the resulting oligomers and co-oligomers by molar percentage even at a high extent of the reaction of IPA/TPA with bisphenols was performed by a combination of GPC and NMR. It was shown that to obtain favorable results in the polycondensation, the next bisphenols should react with the oligomers fairly independently of their chain lengths.

Copolymerization of olefins (ethylene and propylene) and 5-hexen-1-ol pretreated with alkylaluminum was performed using zirconocene/methylaluminoxane catalyst. The influence of the structure of alkylaluminum (as a masking reagent, additive, and cocatalyst) on polymerization behavior was investigated. The physical properties of the copolymers containing 5-hexen-1-ol were also evaluated.

Model systems are developed for quantifying the infrared and Raman spectroscopic properties of copolymers based on poly(styrene-co-divinylbenzene). Analytical curves appropriate for the quantification of para- and metasubstituted species and pendant double bonds are reported, and corrections to previously reported spectroscopic assignments and analytical methods are made. The usefulness of these two analytical methods in characterizing radiation-grafted films and commercial copolymers is compared, and typical characterization results are given. The relative concentrations of the species found in the grafted films are quite different from their concentrations in the grafting solution, and empirical relationships between the two are developed. In addition, the graft composition varies as a function of the base polymer film thickness and type and the penetration depth in the grafted film. Radiation-grafted films are more highly crosslinked in their near surface regions, and thinner films are more extensively crosslinked.

Photopolymerization of 2-hydroxyethyl methacrylate was carried out in ethanol initiated by 2-(N,N-diethyldithiocarbamyl)isobutyric acid as a new water- and alcohol-soluble iniferter under UV irradiation. This polymerization proceeded with a controlled radical mechanism. This system also could be applied to the architecture of amphiphilic block copolymers.

X-ray photoelectron spectroscopy and attenuated total reflectance have been used to study the distribution of melamine in polyester–melamine thermoset coatings. When the melamine concentration is greater than a critical value of 20 wt %, melamine is enriched at the air–coating interface, and it is depleted at the coating–substrate interface, in comparison with the theoretical bulk composition. A physical model has been proposed to explain this phenomenon. It suggests that surface properties can be modified through the control of the composition and cure conditions, by which an appropriate amount of excess melamine can be segregated to the surface and crosslinked.

Crosslinked styrene (St)/maleic anhydride (MA) copolymers were synthesized and functionalized with dicarboxylic acid and dihydroxyphosphino functionalities. The complexation behavior of these functionalized copolymers toward metal ions was studied. The adsorption of Pb(+2) on the dihydroxyphosphino-functionalized St–MA copolymer fit the Langmuir isotherm, and the kinetics fit the rate equation of the moving boundary model, t = [1 − 3(1 − X)^2/3 + 2(1 − X)], where X is the fractional conversion.

A dramatic improvement in the molecular weight characteristics of the polyethers, via a newly developed melt transetherification strategy, was realized with a new catalyst, pyridinium camphorsulfonate (PCS). The improved molecular weights and narrower polydispersity were ascribed to the absence of side reactions possibly arising out of an ether–ether exchange process, which was shown to be significantly slower in model reactions with PCS as the catalyst instead of p-toluenesulfonic acid.

Copolymers of isobutyl methacrylate (i-BMA), and lauryl methacrylate (LMA), were prepared by free-radical solution copolymerizations. Monomer reactivity ratios and corresponding JCIs for TUM and PUM are obtained from low conversion data with NLLS analysis based on Marquardt optimization method. For both copolymerization models, the monomer reactivity ratios that are obtained from integral approach are more reliable than the values obtained from differential approach. Results from the F-statistics test indicated that the PUM offered some improvements over TUM for copolymer composition. In high conversion experiments, the optimal initial feed compositions are obtained in a sequential procedure based on van Herk method. Both accuracy and precision are strongly improved by combining data sets obtained from experiments at different initial monomer feed compositions.

Considering the current theories for propagation and termination steps in copolymerization reactions and using the homopolymerization kinetic coefficients, we have found good qualitative agreement between experimental and theoretical k_p/k values (where k_p and k_t are the average copolymerization propagation and termination rate constants, respectively).

A facile route to synthesis novel poly(amide-imide)s through convenient polycondensation method has been described. This is accomplished by synthesizing a new diacid diimide monomer with mesitylene moieties. A series of poly(amide-imide)s were synthesized with different diamines and they are characterized for solubility, thermal, optical and dielectric properties and were discussed with relevance to the diamine structure. The final polymer exhibited better solubility in most of the organic solvents without much compromise on their thermal stabilities. The dielectric constants were calculated from two different methods namely optical and capacitance method and were compared.

We prepared new semiaromatic polyimides from alicyclic dianhydrides and aromatic diamines containing adamantyl and biadamantyl units. Polycondensations were performed in 1-methyl-2-pyrrolidinone at room temperature for 7 h and then 80 °C for 23 h, giving poly(amic acid)s with inherent viscosities up to 0.58 dL/g. Poly(amic acid)s were converted to corresponding poly(imide)s by thermal treatment. Poly(imide)s showed relatively high thermal stability (5% weight loss around 450 °C) and low dielectric constants (2.69–2.79).

Hybrid organic–inorganic materials derived from 3-glycidoxypropyltrimethoxylsilane (GPTMS) were prepared via two different synthetic routes: (1) the HCl-catalyzed sol–gel approach of silane followed by the lithium perchlorate (LiClO₄)/HCl-catalyzed opening of epoxide and (2) the simultaneous gelation of tin/LiClO₄-catalyzed silane/epoxide groups. The different synthetic routes significantly affected the polymerization behaviors of the organic and inorganic sides in the presence of LiClO₄. A larger amount of LiClO₄ promoted the ring opening of epoxide and led to the formation of longer poly(ethylene oxide) (PEO) chains via the HCl-catalyzed sol–gel approach, whereas in the case of the tin-catalyzed approach, the faster polymerization of the inorganic side hindered the growth of the organic network. The addition of LiClO₄ was proven to be without crystalline salt present in the hybrid networks by wide-angle X-ray powder diffraction. Also, the interactions between the ions and hybrid host, examined with Fourier transform infrared and ⁷Li proton-decoupled magic-angle-spinning NMR, further demonstrated that extensive ion aggregation existed in these hybrid materials.

The association behavior of telechelic hydrogen-bonded poly(ether ketone) (PEK) and polyisobutylene (PIB) polymers and the formation of a new class of pseudo-block copolymers is reported. The attachment of complementing hydrogen bonds (thymine/2,6-diaminotriazine and cytosine/2,6-diaminotriazine) onto the respective PIB and PEK polymers leads to a dramatic increase in the miscibility between the normally immiscible PEK and PIB polymers. The structure formation in the liquid state was studied by dynamic NMR spectroscopy as well as in the solid state via solid-state NMR-spectroscopy, DSC, and TEM methods. The polymers form a nanophase structure with a periodicity of 70 nm with the microphase separation occurring specifically within the donor–acceptor pair with the higher binding constant (thymine/2,6-diaminotriazine) and not within the weaker bonded cytosine/2,6-diaminotriazine pair.

Batch free radical polymerization of 1-vinyl-2-pyrrolidone (VP) in supercritical carbon dioxide was studied in the presence of a reactive polysiloxane surfactant (PDMS-mMA) and AIBN as a free radical initiator. Preliminary investigation of the phase behavior of the polymerization mixture was performed. Polymerization experiments carried out with surfactant concentration in the range of 5.0–12.5% w/w with respect to the monomer proceed with a fast kinetics and lead to the formation of spherical nanoparticles with almost quantitative yields. The effect of the concentration of the surface active macromonomer, the initiator, the monomer, and of the density of the fluid phase on the kinetics of the process and on the morphology of the particles was investigated. Collected experimental results suggest that the polymerization of VP in the presence of PDMS-mMA could proceed with a nucleation mechanism different from that postulated in pure dispersion polymerization stabilized by graft-forming surfactants.

A new oligomeric calix[4]arene-thiacrown-4 (5) was synthesized via a condensation reaction of 5,11,17,23-tetra-tert-butyl-25,27-bis-(4-aminobenzyloxy)-calix[4]arene-thiacrown-4 (4) with adipoyl dichloride. Its extraction ability was also investigated for selected transition metals Cu²⁺, Co²⁺, Cd²⁺, Ni²⁺, Hg²⁺, and Pb²⁺.

A new reactive macromolecular intermediate, polyphosphazene azides, was obtained from poly(dichlorophosphazene) by the direct nucleophilic substitution reaction. This intermediate is very stable in the air, and can be conserved for a long time. As azides have special reactivity, it is believed that many other polyphosphazenes can be easily prepared from this stable intermediate. In this article, the new intermediate was successfully applied to the synthesis of the first C₆₀-containing polyphosphazenes.

The synthesis of perfectly alternating fluorinated polyimide–fluorinated polyhybridsiloxane block copolymers (FPI-FPHSX) was achieved through polyhydrosilylation of α,ω-diallylfluorinated polyimides (AT-FPI) and α,ω-dihydrosilane fluorinated–polyhybridsiloxanes (HT-FPHSX). Three FPI-FPHSX containing 15, 38, and 56 wt % of polyimide were synthesized and characterized. The influence of the soft and hard segment lengths on the properties of FPI-FPHSX block copolymers were also reported.

The synthesis and radical polymerization of ionic liquids based on 1-vinyl imidiazole are described that led to a new family of poly(1-vinyl-3-alkyl-imidazolium) halides. Interestingly, the solubility of these polymers is easily tuned by a simple anion-exchange reaction. With this method new polyelectrolytes soluble in a variety of organic solvents such as acetone, 2-butanone, and tetrahydrofuran are easily prepared.