The Preparation of Ipns of Polystyrene-Polyethylene and Poly(Butyl Methacrylate)-Polyethylene and Their Dynamic Mechanical Behavior

IPNs based on polyethylene and vinyl polymers were prepared according to a new procedure. We studied the dynamic mechanical behavior of two series of IPNs: polystyrene (PS)-polyethylene (PE) and poly(butyl methacrylate) (PBMA)-PE at the frequency ω = 1 Hz and in the temperature region from ?50 to 200°C. Temperature dependences of the components of the dynamic modulus of elasticity G' and G" of the networks PS and PBMA have shapes typical of amorphous networks; the corresponding dependences of pure PE show, however, features typical of a semicrystalline polymer. IPNs of the system PS/PE show two-phase behavior. At T < 110°C, PE functions as a plasticizer. In the system PBMA/PE, better miscibility of components is seen, and PE exerts a reinforcing effect on the mechanical behavior over the whole temperature region. In both systems, network density increases with increasing PE content in IPNs. Better homogeneity and a slight increase in the network density of IPNs with PBMA/PE in comparison to PS/PE networks are probably caused by a greater number of grafted PBMA chains in the PE network compared to the PS network.     

Morphology of micron-sized monodispersed composite polymer particles produced by seeded polymerization for the dispersion of highly monomer-swollen polymer particles

 Monodispersed polystyrene (PS)/poly(n-butyl methacrylate) (PBMA) composite particles having 9.4 μm in diameter were produced by seeded polymerization for the dispersion of highly n-butyl methacrylate (BMA)-swollen PS particles, and their morphologies were examined. The highly BMA-swollen PS particles (about 150 times the weight of the PS seed particles) were prepared by mixing monodispersed 1.8 μm-sized PS seed particles and 0.7 μm sized BMA droplets prepared with an ultrasonic homogenizer in ethanol/water (1/2, w/w) medium at room temperature. After NaNO₂ aqueous solution as inhibitor was added in the dispersion, the seeded polymerization was carried out at 70 °C. In an optical microscopic observation, one or two spherical high contrast regions which consisted mainly of PS were observed inside PS/PBMA composite particles. In the PS domain, there were many fine spherical PBMA domains. Such morphologies were based on the phase separation of PS and PBMA within the homogeneous swollen particles during the seeded polymerization. Received: 04 June 1997 Accepted: 27 August 1997     

The synthesis of diene – alkyl methacrylate diblock and heteroarm star copolymers

The synthesis of A₂B₂ heteroarm stars, where A is either polyisoprene (PI) or polybutadiene (PB) and B is either poly(methyl methacrylate) (PMMA) or poly(butyl methacrylate) (PBMA) has been achieved using living anionic polymerization. Following polymerization of the diene in hexane by sec‐BuLi, the solvent was changed to THF and the living chains were linked in pairs – without loss of anionic reactivity – using 1,2‐bis[4‐(1‐phenylethenyl)]ethane (EPEB). Star synthesis was completed by the addition of MMA or BMA monomer at −78°C. The diblocks were prepared by sequential polymerization. The resulting stereochemistries were those of greatest interest from a practical standpoint, i.e., PI or PB with a high 1,4‐content (which is highly elastic) and syndiotactic PMMA (which has a high T_g).     

Synthesis of nanocylinders consisting of graft block copolymers by the photo‐induced ATRP technique

Photoinduced atom transfer radical polymerizations (ATRP) of t‐butyl methacrylate (BMA) were carried out, initiated by model initiator benzyl N,N‐diethyldithiocarbamate (BDC) in the presence of CuCl/bipyridine (bpy) under UV irradiation. We performed the first‐order time‐conversion plots in this polymerization system, and the straight line in the semilogarithmic coordinates indicated a first‐order in the monomer. The molecular weight of poly(t‐butyl methacrylate) (PBMA) increased in direct proportion to monomer conversion. The molecular weight distribution (M_w/M_n) of PBMA was about 1.3. The initiator efficiency, f, was close to 1.0, which indicated that no side reactions occurred. A copper complex, CuCl/bpy, reversibly activated the dormant polymer chains via a N,N‐diethyldithiocarbamate (DC) transfer reaction such as Cu(DC)Cl/bpy, and it was dynamic equilibrium that was responsible for the controlled behavior of the polymerization of BMA. On the basis of this information, we established a preparation method of nanocylinders consisting of graft block copolymers by grafting from photoinduced ATRP of multifunctional polystyrene having DC pendant groups with vinyl monomers [first monomer, BMA; second monomer, styrene or methyl methcrylate (MMA)]. We have carried out the characterization of such nanocylinders in detail. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 63–70, 2005     

Block copolymers of dodecafluoroheptyl methacrylate and butyl methacrylate by RAFT miniemulsion polymerization

Reversible addition‐fragmentation chain transfer (RAFT) miniemulsion polymerization of butyl methacrylate (BMA) and dodecafluoroheptyl methacrylate (DFMA) was carried out with 2‐cyanoprop‐2‐yl dithiobenzoate (CPDB) as chain transfer agent (CTA). Concentration effects of RAFT agent and initiator on kinetics and molecular weight were investigated. No obvious red oil layer (phase's separation) and coagulation was observed in the first stage of homopolymerization of BMA. The polymer molecular weights increased linearly with the monomer conversion with polydispersities lower than 1.2. At 75 °C, the monomer conversion could achieve above 96% in 3 h with [momomer]:[RAFT]:[KPS] = 620:4:1 (mole ratio). The results showed excellent controlled/living polymerization characteristics and a very fast polymerization rate. Furthermore, the synthesis of poly(BMA‐b‐DFMA) diblock copolymers with a regular structure (PDI < 1.30, PMMA calibration) was performed by adding the monomer of DFMA at the end of the RAFT miniemulsion polymerization of BMA. The success of diblock copolymerization was showed by the molecular weight curves shifting toward higher molar mass, recorded by gel permeation chromatography before and after block copolymerization. Compositions of block copolymers were further confirmed by ¹H NMR, FTIR, and DSC analysis. The copolymers exhibited a phase‐separated morphology and possessed distinct glass transition temperatures associated with fluoropolymer PDFMA and PBMA domains. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1585–1594, 2007     

Morphology of micron-sized monodispersed poly(butyl methacrylate)/polystyrene composite particles produced by seeded dispersion polymerization

In order to develop the seeded dispersion polymerization technique for the production of micron-sized monodispersed core/shell composite polymer particles the effect of polymerization temperature on the core/shell morphology was examined. Micron-sized monodispersed composite particles were produced by seeded dispersion polymerizations of styrene with about 1.4-μm-sized monodispersed poly(n-butyl methacrylate) (Pn-BMA) and poly(i-butyl methacrylate) (Pi-BMA) particles in a methanol/water (4/1, w/w) medium in the temperature range from 20 to 90 °C. The composite particles, PBMA/polystyrene (PS) (2/1, w/w), consisting of a PBMA core and a PS shell were produced with 2,2′-azobis(4-methoxy-2,4-dimethyl valeronitrile) initiator at 30 °C for Pn-BMA seed and with 2,2′-azobis(isobutyronitrile) initiator at 60 °C for Pi-BMA seed. The polymerization temperatures were a little above the glass-transition temperatures (T _g) of both Pn-BMA (20 °C) and Pi-BMA (40 °C). On the other hand, when the seeded dispersion polymerizations were carried out at much higher temperatures than the T _g of the seed polymers, composite particles having a polymeric oil-in-oil structure were produced. Received: 14 October 1998 Accepted in revised form: 2 June 1999     

Dual monomer grafting of styrene and maleic anhydride onto model hydrocarbon substrates

Styrene and maleic anhydride (MAn) were successfully grafted, alone and simultaneously, onto various model hydrocarbon substrates at 180 °C with 2,5‐dimethyl‐2,5‐di‐(t‐butyl peroxy)hexane (L101) as a free‐radical initiator. Dodecane, 1‐dodecene, and 2,6,10,14‐tetramethylpentadecane were selected as model compounds to investigate the effects of terminal unsaturation and branching on grafting and crosslinking. These compounds were chosen to mimic the aforementioned microstructural characteristics that are commonly observed in polyethylene. The results demonstrate that terminal unsaturation increases the amount of crosslinked material in the presence of L101. With respect to grafting, for the single monomer systems, MAn prefers to graft as single saturated units, whereas styrene prefers to graft as long chains of polystyrene oligomers. However, when both monomers are grafted simultaneously, graft yields are drastically reduced because of a propensity for the two monomers to form a styrene–maleic anhydride copolymer. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2456–2468, 2000     

Influence of particle diameter on the morphology of micron-sized, monodispersed composite polymer particles produced by seeded polymerization for the dispersion of highly monomer-swollen polymer particles

 Micron-sized, monodispersed polystyrene (PS)/poly (n-butyl methacrylate) (PBMA) composite particles, in which the PS domain(s) were dispersed in a PBMA continuous phase, were produced by seeded polymerization for dispersions of n-butyl methacrylate (BMA) swollen PS particles in a wide range of PS/BMA ratios in the presence of NaNO₂ as a water-soluble inhibitor. Moreover, in order to change the diameter of the composite particles at same PS/BMA ratio, PS/PBMA (1/150 w/w) composite particles were produced using five kinds of PS particles in a range of diameters from 0.64 to 3.27 μm as seeds. The percentages of the PS/PBMA composite particles having double and triple and over PS domains, which were thermodynamically unstable morphologies, increased with the increase in the diameter of BMA swollen PS particles. There was a clear influence of the size of the swollen particles on the morphology of the PS/PBMA composite particles produced. Received: 30 September 1999/Accepted: 18 April 2000     

Influence of the swelling state of seed polymer particles with monomer on the morphology of micron-sized monodispersed composite polymer particles produced by seeded polymerization utilizing the dynamic swelling method

 Micron-sized mono-dispersed polystyrene (PS)/poly(n-butyl methacrylate) (PBMA) composite particles (PS/PBMA=2/1 by weight) having a heterogeneous structure in which many fine PBMA domains dispersed in a PS matrix near the particle surface were produced by seeded polymerization of n-butyl methacrylate (BMA) of which almost all had been absorbed by 1.8 μm-sized monodispersed PS seed particles utilizing the dynamic swelling method. The morphology was varied by changing the PS/BMA ratio and polymerization temperature. It was concluded that the swelling state of 2 μm-sized BMA-swollen PS particles in the seeded polymerization process is one of the important factors to control the morphology of the composite particles. Received: 27 November 1996 Accepted: 21 March 1997     

Grafting of Polymers onto Activated Carbon Surface: Graft Polymerization of Vinyl Monomers Initiated by Azo Groups That Were Introduced onto the Surface

Abstract

We examined the grafting of polymers onto an activated carbon powder surface by polymerization that was initiated by azo groups that were introduced onto the surface as well as the effects of grafted polymers on the adsorption of acetic acid. The introduction of azo groups onto the surface was achieved by the following methods: (1) a reaction of 4,4′-azobis(4-cyano-pentanoic acid) (ACPA) with surface isocyanate groups that were introduced beforehand by treatment with tolylene 2,4-diisocyanate (AC-Azo 1) and (2) the direct condensation of ACPA with surface phenolic hydroxyl groups by using N,N'-dicyclohexylcarbodiimide (AC-Azo 2). The radical polymerizations of styrene, methyl methacrylate, N,N-diethylacrylamide (DEAM), and N-isopropylacrylamide (NIPAM), were successfully initiated by the azo groups on the surface and the corresponding polymers were grafted onto the surface. There was a significant decrease in the adsorption of the acetic acid of the activated carbons when polymers were grafted onto them, particularly in regards to the grafting of hydrophobic polymers. On the other hand, a decrease in the adsorbability of the polyDEAM-grafted and polyNIPAM-grafted activated carbon was barely observed. In addition, polyDEAM-grafted and polyNIPAM-grafted activated carbons showed temperature-dependent adsorption of acetic acid: the adsorbability of these activated carbon decreased above lower critical solution temperature of these polymers, which is about 32°C.     

Preparation of soluble and fusible poly(2,5-dimethoxy-1,4-phenylene)

Poly(2,5-dimethoxy-1,4-phenylene) was prepared by oxidative polymerization of p-dimethoxybenzene with aluminum chloride and copper(II) chloride in nitrobenzene under reduced pressure. The polymers obtained were soluble in sulfuric acid and fusible at 320°C. The intrinsic viscosity of the polymer was ca. 0.07 in sulfuric acid. Demethylation of methoxy groups did not occur during the polymerization.     

Synthesis,characterization, and stability of carbodiimide groups in carbodiimide‐functionalized latex dispersions and films

Cyclohexylcarbodiimidoethyl methacrylate (CCEMA) and t‐butylcarbodiimidoethyl methacrylate (t‐BCEMA) were prepared in a two‐step synthesis. These monomers were then used to prepare carbodiimide‐functionalized PBMA and PEHMA latex particles, employing two‐stage emulsion polymerization, with the carbodiimide–methacrylate monomers being introduced only in the second stage under monomer‐starved conditions. During emulsion polymerization, the carbodiimide moiety ( NCN ) was found to be unstable at pH 4, but stable when the pH of the dispersion was increased to 8, using NaHCO₃ as the buffer. Survival of  NCN group against hydrolysis during the polymerization, and during storage in the dispersion, was enhanced by using EHMA as the comonomer (more hydrophobic) and the t‐butyl carbodiimide derivative. The t‐butyl group provides more steric hindrance to the hydrolysis reaction. A decrease in the reaction temperature from 80°C to 60°C was also found to increase the extent of  NCN group incorporation during emulsion polymerization. Under ideal conditions, more than 98% of the  NCN groups in the monomer feed are successfully incorporated into the latex. When these latex particles are mixed with a  COOH containing latex and allowed to dry, polymer diffusion leading to crosslinking occurs. Films annealed at 60°C reach a gel content of 60% in 10 h. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 855–869, 2000     

Grafting of methacrylates and styrene on to polystyrene backbone via a “grafting from” ATRP process at ambient temperature

Well defined graft copolymers are prepared by “grafting from” atom transfer radical polymerization (ATRP) at room temperature (30 °C). The experiments were aimed at grafting methacrylates and styrene at latent initiating sites of polystyrene. For this purpose, the benzylic hydrogen in polystyrene was subjected to allylic bromination with N‐bromosuccinimide and azobisisobutrylnitirle to generate tertiary bromide ATRP initiating sites (Br? C? PS). The use of Br? C? PS with lesser mol % of bromide initiating groups results in better control and successful graft copolymerization. This was used to synthesize a series of new graft copolymers such as PS‐g‐PBnMA, PS‐g‐PBMA, PS‐g‐GMA, and PS‐g‐(PMMA‐b‐PtBA) catalyzed by CuBr/PMDETA system, in bulk, at room temperature. The polymers are characterized by GPC, NMR, FTIR, TEM, and TGA. Graft copolymerization followed by block polymerization enabled the synthesis of highly branched polymer brush, in which the grafting density can be adjusted by appropriate choice of bromide concentration in the polystyrene. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3818–3832, 2007     

Crosslinking of polyimides via spirodilactone unit in polymer backbone

A new approach for the crosslinking of polyimides via the lactamization of spirodilactone unit in polyimide backbone was studied by two means: model reaction and the comparison of the properties of the polyimide precursors to those of the crosslinking polymers. Polyimides 4 and 5 were soluble in N,N′dimethylacetamide (DMAc), dimethylformamide (DMF), dimethylsulfoxide (DMSO), N′-methylpyrrolidone (NMP), and other common organic solvents, whereas their corresponding crosslinking polymers were insoluble in these solvents. The glass transition temperatures for polyimide 5 and its crosslinking polymer were 262°C and 291°C, whereas those for polyimide 4 and its crosslinking polymer were 265°C and 360°C. The weight-loss rate of the crosslinking polymers was apparently slower than that of the precursors when the temperature was > 400°C. The 10% weight-loss temperature for the polyimides 4 and 5 was < 500°C, whereas that for the crosslinking polymers was close to or above 600°C. The results indicate that this type of crosslinking polymer has good thermal properties. The temperature for the formation of lactam was above 180°C. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3680–3686, 1999     

Foamed crosslinked LDPE/PP blends made by hot mold injection molding

Foamed and crosslinked blends of LDPE and i-PP were investigated. The specimens were made by hot mold injection molding process at the temperature of the mold of 210°C. Azodicarbonamide as foaming agent and 2,5-dimethyl-2,5-di(tert.-butylperoxy)hexane as crosslinked agent were used. The chemical changes as a result of the crosslinking were determined by gel content. Thermal behavior of the blends was studied by DSC. The difference of influence of crosslinking agent on chemical changes of both polymers was established. An improvement of the mechanical properties due to crosslinking between PE and PP on their interface was observed. The interaction on the PE/PP interface was confirmed by phase transition parameters determined on the basis of DSC-curves.     

Higher aliphatic polyaldehydes. IV. Transitions in poly(n-valeraldehyde), poly(n-hexaldehyde), poly(n-heptaldehyde), and poly(n-octaldehyde)

Crystalline polymers of n-valeraldehyde, n-hexaldehyde, n-heptaldehyde, and n-octaldehyde were prepared by anionic polymerization with lithium tertiary butoxide as the initiator at low temperatures. The polymers were end-capped with acetic anhydride, and their thermal stability was studied primarily by DTG. It was found that all polymers degrade rapidly above 150°C. All polymers show a dual melting-point behavior. The first melting region, which is associated with the melting of the side chain, is 80–85°C for poly(n-valeraldehyde); 87–90°C for poly(n-hexaldehyde); 78–101°C for poly(n-heptaldehyde); and 41–69°C for poly(n-octaldehyde). Annealing and quenching of the samples showed that this melting-point region consisted of several endotherm peaks whose intensity changed according to the thermal history of the sample. Although the samples are apparently highly crystalline, the side-chain crystallinity is apparently only in the 20% range.     

Influence of viscosity within polymerizing particle on the morphology of micron-sized,monodisperse composite polymer particles produced by seeded polymerization for the dispersion of highly monomer-swollen polymer particles

Micron-sized, monodisperse polystyrene (PS)/poly( n-butyl methacrylate) (PBMA) composite particles, in which PS domain(s) were dispersed in a PBMA continuous phase, were produced by seeded polymerization for the dispersion of highly n-butyl methacrylate (BMA)-swollen PS particles (PS/BMA=1/150, w/w) using various concentrations of benzoyl peroxide as initiator in the absence/presence of sodium nitrite (NaNO ₂) as a water-soluble inhibitor. The percentages of the composite particles having double, triple and over PS domains, which were thermodynamically unstable morphologies, increased with a rapid increase of viscosity within the polymerizing particle.     

Synthesis and polymerization studies of 1,2-dimethyleneoctafluorocyclohexane

1,2-Dimethyleneoctafluorocyclohexane has been prepared by the pyrolysis of 2-chloro-methyl-1-methyloctafluorocyclohexane. Free radicals initiate the polymerization of the diene in both bulk and emulsion systems to give a highly crystalline (mp 214–218°C) polymer that has an all-cis 1,4-structure. The polymer is insoluble in common laboratory solvents, but will dissolve in perfluorokerosene above 175°C and in 2,5-dichlorobenzo-trifluoride above 150°C. This diene is not polymerized by cationic, anionic, or Ziegler-Natta catalysts. The diene is readily copolymerized with many common monomers to give soluble, high molecular weight polymers. Relative reactivity ratios have been measured with styrene by the Fineman and Ross method and Q–e parameters for the diene have been calculated.     

Radical copolymerization of fullerene (C60) and n‐butyl methacrylate (BMA) using triphenylbismuthonium ylide and characterization of C60–BMA copolymers

Radical copolymerization of fullerene (C₆₀) and n‐butyl methacrylate (BMA) has been carried out using triphenylbismuthonium ylide as an initiator at 70°C for 4 h in a dilatometer under nitrogen atmosphere. The kinetic expression of the polymerization is R_pα [Ylide]^0.5[C₆₀]^?1.0[BMA]^1.2, which is similar to that expected for ideal kinetics. The rate of polymerization increases with an increase in the concentration of initiator and BMA. However, it decreases with an increase in the concentration of fullerene. Fullerene acts as radical scavengers causing retardation in polymerization. The activation energy of copolymerization was estimated to be 72.2 K J mol^?1. The fullerene‐containing BMA copolymers were characterized by FTIR, ¹H NMR, ¹³C NMR, UV–vis, and GPC analyses. © 2011 Wiley Periodicals, Inc. Int J Chem Kinet 43: 608–619, 2011     

Free radical initiated low temperature crosslinking of phenylethynyl (PE) end‐capped oligomides

A relatively low‐temperature crosslinking method for phenylethynyl (PE) end‐capped oligomides was developed. PE end‐capped oligomides are typically cured into crosslinked polyimides at 370 °C for about 1 h. The addition of a low viscosity mixed‐solvent of N‐methylpyrrolidinone (NMP)/dimethyl ether of polyethylene glycol (M = 250 g/mol), NMP/DM‐PEG‐250, or NMP/polyethylene glycol (M = 400 g/mol), NMP/PEG‐400, as film forming medium for PE‐end‐capped oligomides was investigated. Fourier transform infrared spectroscopy and ¹³C NMR showed that the mixed solvent addition was effective for achieving low‐temperature crosslinking of the ethynyl end‐caps over the temperature range 200–250 °C. The low temperature crosslinking process was explained by thermolysis of the PEG molecules over this temperature range forming free radical species such as ～CH₂CH₂O· or ～CH₂CH₂^· which initiate cure of the ethynyl groups resulting in a cross linked polyimide membrane. The PEG solvents also provide a radical source for the degradation polymerization of the solvents to a water and NMP insoluble polymer, which formed a miscible blend with the crosslinked membrane. Glass transition temperature (differential scanning calorimetry) data and thermo gravimetric analysis data provide evidence for the miscible blend. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3950–3963, 2010.