Ethylene/POSS copolymerization behavior of postmetallocene catalysts and copolymer characteristics

Copolymerization of ethylene with iso‐butyl substituted monoalkenyl(siloxy)‐ or monoalkenylsilsesquioxane (POSS) comonomers over bis(phenoxy‐imine) and salen‐type titanium and zirconium catalysts was studied. It was found that the polyreaction performance was significantly depended by the kind of the catalyst and by the structure and concentration of POSS in the feed. The POSS comonomer was efficiently incorporated into the polymer chain at up to 0.2 mol %. The differences in the copolymer compositions as the functions of the catalyst kind and the POSS comonomer were observed, including the varied number‐average sequence length of ethylene and unsaturated end groups, as determined by ¹H NMR and FT‐IR. The presence of POSS comonomers affected also the melting and crystallization behavior of the copolymers, as evidenced by DSC, because of influence on the polymer chain arrangement. The POSS units could act as the nucleating agents. Moreover, the crystal and structural parameters of ethylene/POSS copolymers were evaluated on the basis of X‐ray results, and the limited self‐aggregation of POSS incorporated into the polymer chain, the small number and size of POSS aggregates, and the increased crystallinity degree of copolymers were demonstrated. The ethylene/POSS copolymers produced by postmetallocenes offered also high thermal stability and interesting morphological properties. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3918–3934     

Head-to-head vinyl polymers. IV. Preparation and characterization of equimolar head-to-head copolymers of acrylic acid and its esters

The alternating copolymer of ethylene with maleic anhydride was esterified with a number of aliphatic alcohols to yield its monoesters, which correspond structurally to equimolar (1:1) head-to-head (h-h) copolymers of acrylic acid with alkyl acrylates. In addition, they were methylated with diazomethane to 1:1 h-h copolymers of methyl acrylate with alkyl acrylates. For comparison the 1:1 head-to-tail (h-t) copolymers of methyl acrylate with alkyl acrylates were prepared by radical copolymerizations. Some chemical, physical, and thermal properties of these 1:1 h-h and h-t copolymers were evaluated and compared. The softening and glass transition temperatures of the 1:1 h-h copolymers were somewhat higher than those of the corresponding 1:1 h-t copolymers, which indicated that the h-h replacements made the polymer chain stiffer and less flexible. The 1:1 h-h copolymers were also observed to degrade thermally at somewhat higher temperatures and with higher rates than the 1:1 h-t copolymers. The ratio of alcohol to monomer found in the pyrolysis products was higher for the 1:1 h-h than for its respective 1:1 h-t copolymer.     

Investigation of the synthesis of poly-D,L-lactide-co-poly(ethylene glycol) flexible thermoplastic

A series of biodegradable poly(D,L-lactide)-poly(ethylene glycol) multiblock poly(ether-ester-urethane)s with various lactide-to-poly(ethylene glycol) (LA/PEG) mole ratios has been successfully synthesized by ring-opening polymerization (ROP) followed by chain extension reaction through formation of urethane linkage. Resulting FT-IR spectra indicate complete polymerization of lactide monomers, while NMR analysis quantitatively marks the chain length of polymer blocks. The molecular weight and dispersion index of copolymers were investigated by GPC analysis. DSC thermogram and XRD diffractogram of the prepared copolymers were studied as well for revealing the thermal and crystallinity behavior of the copolymer as LA/PEG mole ratios varied.     

Docosyl acrylate modified polyacrylic acid: synthesis and crystallinity

Copolymers of n-docosyl acrylate and acrylic acid were synthesized in tetrahydrofuran by conventional free radical polymerization using benzoyl peroxide as initiator. The increase in crystallinity of the copolymers with increasing C₂₂ acrylate mole fraction was studied. It was found that even with very low mole fraction of C₂₂ acrylate (0.14) in the polymer chain the copolymers shows significant crystallinity (crystallinity fraction 0.23 against 0.52 for homopolymer of C₂₂ acrylate).     

Synthesis and characterization of anionic graft copolymers containing poly(ethylene oxide) grafts

Anionic graft copolymers were synthesized through grafting of poly(ethylene glycol) monomethyl ether (MPEG) onto terpolymers containing succicinic anhydride groups. The backbone polymers were prepared through radical terpolymerization of maleic anhydride, styrene, and one of the following monomers: methyl methacrylate, ethylhexyl methacrylate, and diethyl fumarate. MPEG of different molecular weights were grafted onto the backbone through reactions with the cyclic anhydride groups. In this reaction one carboxylic acid group is formed together with each ester bond. The molecular weights of MPEG were found to influence the rate of the grafting reaction and the final degree of conversion. The graft copolymers were characterized by IR, GPC, and ¹H-NMR. Thermal properties were examined by DSC. Graft copolymers containing 50% w/w of MPEG 2000 grafts were found to be almost completely amorphous, presumably because of crosslinking, and hydrogen bonding between carboxylic acid groups in the backbone and the ether oxygens in MPEG grafts. © 1995 John Wiley & Sons, Inc.     

Synthesis and bulk assembly behavior of linear–dendritic rod diblock copolymers

Dendritic rod structures can be formed via the branching of dendritic elements from a primary polymer backbone; such systems present an opportunity to create nanoscale material structures with highly functional exterior regions. In this work, we report for the first time the synthesis of a hybrid diblock copolymer possessing a linear–dendritic rod architecture. These block copolymers consist of a linear poly(ethylene oxide)–poly(ethylene imine) diblock copolymer around which poly(amido amine) branches have been divergently synthesized from the poly(ethylene imine) block. The dendritic branches are terminated with amine or ester groups for the full generations and half‐generations, respectively; however, the methyl ester terminal groups can also be readily converted into alkyl groups of various lengths, and this allows us to tune the hydrophilic/hydrophobic nature of the dendritic block and, therefore, the amphiphilic properties of the diblock copolymer and its tendencies toward microphase separation. The block copolymers exhibit semicrystallinity due to the presence of the poly(ethylene oxide) block; however, as the polymer fraction consisting of poly(ethylene oxide) decreases, the overall crystallinity also decreases, and it approaches zero at generation 2.0 and higher. The unfunctionalized block copolymers show weak phase segregation in transmission electron microscopy and differential scanning calorimetry at all generations. The addition of n‐alkyl chains increases phase segregation, particularly at high alkyl lengths. The generation 3.5 polymer with n‐dodecyl alkyl substitution has a rodlike or wormlike morphology consisting of domains of 4.1 nm, equivalent to the estimated cross section of the individual polymer chains. In this case, the nanometer scale of the polymer chains can be directly observed with transmission electron microscopy. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2784–2814, 2004     

Complexed copolymerization of vinyl compounds with alkylaluminum halides

The monomer reactivity in the complexed copolymerization of vinyl compounds with alkylaluminum halides has been extensively surveyed. Equimolar copolymers were obtained in various combinations of monomers which are classified into two monomer groups, A and B. The group B monomers are conjugated vinyl compounds having nitrile or carbonyl groups in the conjugated position and form complexes with alkylaluminum halides. The group A monomers are donor monomers having low values, such as olefins, haloolefins, dienes, and unsaturated esters. These A monomers belong to the same group of monomers which give alternating copolymers in conventional radical copolymerization with maleic anhydride, SO₂, and so on. In addition the complexed copolymerization has the same specific characteristics as the conventional alternating copolymerization, i.e., high reactivities of allyl-resonance monomers and inner olefins and no transfer of halogen atom to the copolymers in CCl₄. These features suggest little or no participation of the A monomer radical. The Q-e scheme is also discussed in terms of the monomer reactivity. More than two monomers selected from groups A and B give multicomponent copolymers in which alternating sequential structures hold with respect to A and B. Anomalous mutual reactivities between two B monomers in the terpolymerization were observed and indicate that the nature of radical in the complexed copolymerization may be different from that expected by the Lewis-Mayo equation. The complexed radical mechanism previously proposed is discussed in connection with the specific behavior mentioned above.     

NMR spectroscopy and free volume analysis of the effects of copolymer composition on the swelling kinetics and chain dynamics of highly crosslinked copolymers of acrylic acid with PEG‐containing multiacrylates

Novel ionizable polymer networks were prepared from oligo(ethylene glycol) (OEG) multiacrylates and acrylic acid (AA), employing bulk radical photopolymerization techniques. The properties of these materials exhibited a complex dependence on the network structure and composition. Penetrant sorption experiments demonstrated that the crosslinked structure of the copolymers depended very strongly on the AA content as well as the number of ethylene glycol groups. The impact of varying the AA content and the oligo(ethylene glycol) chain length on the polymer chain dynamics was examined using diffusion and ¹³C NMR relaxation studies. The penetrant uptake studies indicated a coupling of Fickian and relaxation‐driven contributions to the swelling behavior. The effect of increasing the AA content on the characteristic chain relaxation time was reversed as the oligo(ethylene glycol) chain length was varied, indicating that chain relaxation is controlled by structural considerations, for shorter oligo(ethylene glycol) chains, and by compositional considerations, for longer oligo(ethylene glycol) chains. Measured compositional effects on solid state ¹³C NMR relaxation times supported these conclusions. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1953–1968, 1999     

Controlled radical (co)polymerization of (meth)acrylic esters via the reversible addition-fragmentation chain-transfer mechanism

The homopolymerization of acrylic and fluoroacrylic esters mediated by benzyl dithiobenzoate and dibenzyl trithiocarbonate proceeds in the controlled mode via the reversible addition-fragmentation chain-transfer mechanism, while the controlled radical polymerization of methacrylic esters is not effected under these conditions. The molecular-mass characteristics of the copolymers of acrylic and methacrylic esters may be satisfactorily controlled by benzyl dithiobenzoate-mediated copolymerization when the content of acrylic esters is no less than 50 mol %. If a reversible addition-fragmentation chain-transfer agent active with respect to only one of the monomers is used, compositionally homogeneous narrowly dispersed copolymers are formed via the azeotropic copolymerization of the monomers up to high conversions. The controlled copolymerization of N-vinylpyrrolidone and fluoroacrylates allows the synthesis of alternating narrowly dispersed amphiphilic copolymers with properties different from those of alternating copolymers with a broad molecular-mass distribution.     

N-苯基马来酰亚胺/对氯甲基苯乙烯活性可控超支化交替共聚合的研究

采用核磁共振氢谱, 研究了N-苯基马来酰亚胺(NPMI)与对氯甲基苯乙烯(PCMS)在氘代氯仿中的络合性能. 以PCMS作为引发剂单体, 通过原子转移自由基聚合(ATRP)引发NPMI-PCMS电子转移络合物(CTC)进行活性可控超支化共聚合. 考察了单体初始摩尔分数对共聚物组成和其玻璃化转变温度的影响, 用Kelen-Tudos法计算得到两种单体的竞聚率分别为 r_NPMI＝0.11和r_PCMS＝0.25. 结果表明, 当单体配比f_NPMI＝0.4～0.7时, 共聚物具有交替结构, 其耐热性随着NPMI含量的增加而提高. 此外还考察了溶剂、聚合温度等对共聚合反应动力学的影响. 并进一步用所得超支化交替共聚物作为大分子引发剂, 引发甲基丙烯酸甲酯(MMA)聚合, 制得了多臂超支化接枝共聚物 poly(NPMI-co-PCMS)/poly(MMA).     

Effect of the conformation of the alkyl chain on the catalytic miniemulsion copolymerization of ethylene and acrylates

The catalytic copolymerization of ethylene and acrylic monomers is a promising way of incorporating polar functionality into polyolefins and therefore enlarging the range of properties of these materials. This work shows that for the copolymerization of ethylene and C4 acrylates using a sterically encumbered Pd catalyst, the degree of incorporation of the acrylic monomer decreases with the degree of branching of the alkyl chain of the acrylate, the main reason being the difficulty for coordination of bulky acrylates to the catalytic site. This strongly affects the polymerization rate as well as the molecular weight, crystallinity and melting point temperature of the copolymers.     

乙烯-α-烯烃共聚物的结晶性能及其临界序列结晶长度的研究

本文用DSC、WAXD及偏光显微镜(PLM)方法,研究了化学反应法催化剂合成的乙烯-α-烯烃共聚物的结晶性能及其临界序列结晶长度。结果表明,随共聚物中α-烯烃含量增大,共聚物的微晶尺寸、结晶度及熔点均逐渐减小,而晶胞参数增大。变化的辐度戊烯>辛烯。共聚物的临界结晶序列长度(n)和k值均戊烯<辛烯。上述结果表明影响支链进入晶格的主要因素是α-烯烃支链长度和结构。     

Synthesis and Characterization of Ethylene/Propylene Copolymers in the Whole Composition Range

Summary: The incorporation of comonomer molecules in the backbone of a homopolymer can influence the final properties of the material, decreasing its crystallinity and the melting and glass transition temperatures, and increasing its impact resistance and transparency. In the present work, ten ethylene/propylene copolymers have been synthesized using a supported metallocene catalytic system covering the whole composition range. Any desired composition was obtained by controlling the feed composition during the reaction. These synthesized copolymers have been characterized by different techniques in order to study the effect of the comonomer incorporation onto their final properties. When the comonomer content is low, the behaviour of the copolymer is similar to that of the corresponding homopolymer. Nevertheless, if the comonomer content increases, the copolymer becomes more amorphous (low crystallization temperature and soft XRD signals) and easily deformable, reaching a behaviour close to that corresponding to an elastomeric material. In order to corroborate these results the samples have been characterized by TREF and GPC-MALS. TREF analysis showed that copolymers containing less than 10% and more than 80% of ethylene are semicrystalline, with elution temperatures typical of this kind of polymers. Molecular weights are higher for homopolymers and they decrease as the comonomer concentration increases, whereas the polydispersity index keeps almost constant at the expected value for this kind of samples.     

Synthesis of pH‐sensitive surfactants by the terpolymerization of methacrylic acid,methoxy poly(ethylene glycol) methacrylate,and lauryl methacrylate: Initiator effect and reactivity ratio study

For the development of pH‐sensitive surfactants to be used in water‐in‐oil fermentation, the free‐radical terpolymerization of methacrylic acid (MAA), methoxy poly(ethylene glycol) methacrylate (MPEGMA), and lauryl methacrylate (LMA), at a molar ratio of 1.0:0.04:0.76, was studied with two initiators, azobisisobutyronitrile (AIBN) and hydrogen peroxide, at different concentrations. The polymer synthesized with 0.45% AIBN as the initiator was the most promising, giving similar conversions of all three monomers throughout the 10‐h polymerization. The subsequent study on AIBN‐initiated systems indicated that MPEGMA caused an increase‐then‐decrease profile of the MAA conversion with a plateau around an ethylene glycol/MAA ratio of 1–2. This observation was fairly consistent with the well‐known type II template polymerization of poly(ethylene glycol) (PEG)–MAA systems. The reactivity ratios obtained in this study suggested that the polymer synthesized with AIBN as the initiator had a structure of alternating blocks of MAA and LMA, with isolated PEG grafts. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2950–2959, 2004     

Biospecific Properties of Random Copolymers, 1

The kinetic study of copolymer synthesis is important to understand how a material is built and how it can get some particular properties. The radical copolymerization of one, two or more monomers can be simulated with classical analytic models, but can also be simulated by a Monte Carlo model that allows a bigger flexibility and is a lot easier to compute and use. We have shown that this Monte Carlo simulation gives the same results of the kinetic study of the terpolymerization as the analytic model, and it can create easily a bank of virtual copolymers for all the compositions needed to analyze the structure of the macromolecular chains in terms of sequences of monomers occurring as a function of the global composition. The search for the sequences is very simple to compute as it consists in a simple reading of the virtual chains previously simulated. This result can thus be applied to make appear a simple correlation between the distribution of functional groups and some specific observed biological activities of biospecific copolymers.

Simplified schema of the numerical virtual terpolymerization.     

Interaction of sodium dodecyl sulfate with methacrylate-PEG comb copolymers

A series of sodium methacrylate and poly(ethylene glycol) (PEG) comb copolymers (MAA/PEG) with approximate PEG chain lengths of 7, 11, and 22 ethylene oxide units were synthesized by free radical polymerization. Their weight-average molecular mass was found to be approximately 66 000. A commercial sample of a PEG comb polymer with an acrylic backbone was also used in the studies (Sokalan HP 80). The interaction of the MAA/PEG comb polymers and pure sodium methacrylate (SPMA) with sodium dodecyl sulfate (SDS) was studied by ESR spectroscopy using 5-doxyl stearic acid (5-DSA) spin probe and by conductivity measurements. Surfactant aggregation in water occurred at SDS concentrations lower than the surfactant critical micelle concentration (cmc) and depended on the polymer concentration. The observations have been attributed to changes in the effective ionic strength of the systems due to the polymer itself, and it has been concluded that there is no interaction between the MAA/PEG comb copolymers or SPMA and SDS. This has been confirmed by the fact that the decrease in surfactant aggregation concentration is similar in magnitude to the decrease observed on adding NaCl when counterion ion condensation effects are taken into account. It is apparent that the electrostatic repulsions between the surfactant molecules and the methacrylate backbone of the MAA/PEG comb copolymers inhibit association of SDS with the PEG side chains.     

Structure of ethylene–chlorotrifluoroethylene copolymers

The structures of copolymers of ethylene and chlorotrifluoroethylene have been studied by infrared, nuclear magnetic resonance, and x-ray diffraction techniques. Copolymers varying in ethylene composition from 80 to 50 mole-% were prepared at a number of different temperatures with a peroxide catalyst system. Compositions of 50/50 mole ratio were found to be semicrystalline and to have melting points as high as 241°C. These materials were found to be copolymers with a high degree of one-to-one alternation. They were similar in structure to 1:1 copolymers which had been reported previously by other workers who used a triethylboron catalyst system. The x-ray evidence indicated that the copolymers prepared with the peroxide catalysts were not stereoregular. A hexagonal unit cell with a theoretical density of 1.70 g/cc was determined for the alternating one-to-one copolymer by x-ray techniques. A value of 262°C was determined for the melting point of the theoretical 100% alternating one-to-one copolymer. Values of ΔH_? = 4500 cal/mole and ΔS_? = 8.4 cal/deg-mole were also calculated for the alternating 1:1 copolymer. The preferred conformation of the material appears to be a “kinked” structure with the crystalline phase having ethylene units in one chain lining up opposite chlorotrifluoroethylene units in the adjacent chain. Polar association which can occur between fluorine and hydrogen atoms in this arrangement may account in part for the relatively high melting point of the alternating one-to-one copolymers.     

Organocatalyzed Photo-Controlled Synthesis of Ultrahigh-Molecular-Weight Fluorinated Alternating Copolymers

Ultrahigh-molecular-weight (UHMW) polymers with tailored structures are highly desirable for the outstanding properties. In this work, we developed a novel photoorganocatalyzed controlled radical alternating copolymerizations of fluoroalkyl maleimide and diverse vinyl comonomers, enabling efficient preparation of fluorinated copolymers of predetermined UHMWs and well-defined structures at high conversions. Versatility of this method was demonstrated by expanding to controlled terpolymerization, which allows facial access toward fluorinated terpolymers of UHMWs and functional pendants. The obtained copolymers exhibited attractive physical properties and furnished thermoplastic, anticorrosive and (super)hydrophobic attributes as coatings on different substrates. Molecular simulations provided insights into the coating morphology, which unveiled a fluorous protective layer on the top surface with polar groups attached to the bottom substrate, resulting in good adhesion and hydrophobicity, simultaneously. This synthetic method and customized copolymers shed light on the design of high-performance coatings by macromolecular engineering.     

Graft copolymers having hydrophobic backbone and hydrophilic branches. III. Synthesis of graft copolymers having oligovinylpyrrolidone as hydrophilic branch

Graft copolymers were synthesized by the esterification reaction between acrylic copolymers and carboxyl group terminated vinylpyrrolidone oligomer using phase transfer catalysts. Acrylic copolymers were obtained by the radical copolymerization of β-bromoethyl methacrylate, chloromethylstyrene or glycidyl methacrylate with methyl methacrylate. Hydrophilic oligomers were prepared by the radical oligomerization of vinylpyrrolidone using β-mercaptopropionic acid as chain transfer agent. The degree of esterification increased with decreasing the molecular weight of oligomer and with increasing the number of potential grafting sites on polymer backbones. The water dispersibility of graft copolymers increased with increasing the nitrogen content and was therefore dependent on the branch oligomer content.     

Characterization of Ethylene Copolymers with Liquid Chromatography and Melt Rheology Methods

Summary: Melt rheology and polymer chromatography methods were applied to characterize molecular heterogeneities in products of free radical copolymerization of ethylene with methyl acrylate and vinyl acetate comonomers performed in continuously stirred tank and tubular reactors. We found that the ethylene–vinyl acetate copolymers made in both reactors had similar linear viscoelastic properties typical to branched products of the high pressure process. But the ethylene–methyl acrylate copolymers obtained in the tubular reactor had unusually high melt viscosity at low shear rate and much lower onset of shear thinning despite the narrower molecular weight distribution and the lower overall amount of long-chain branches compare to their autoclave counterparts with similar average molecular weight and chemical composition. Using interaction polymer chromatography method called gradient elution at critical point of adsorption we found that ethylene-acrylate copolymers from the tubular reactor had very broad chemical composition distribution, which was consistent with a significant difference in reactivity ratios between ethylene and acrylate comonomers. Such chemical composition heterogeneity can be a reason for the observed unusual rheological properties of these copolymers.