Microstructure Of Polybutadiene Research Articles

Investigating The Kinetics of Anionic Polymerization of Butadiene in Presence of 1,2‐diethoxypropane Using Online Near‐Infrared Spectroscopy

AbstractOnline near‐infrared spectroscopy technique is employed to investigate the kinetics of the anionic polymerization of butadiene with n‐butyllithium initiator in the presence of the microstructure modifier 1,2‐diethoxypropane (DEP) in cyclohexane solvent. A phenomenological kinetic model is developed to describe the anionic polymerization process in the presence of DEP, and its influence on the microstructure of polybutadiene under different conditions is determined.

Trans-1,4-polybutadiene: Influences of Lewis bases on polymerization of butadiene with supported titanium catalyst systems

Three MgCl2 supported TiCl4 pro-catalysts; Cat-A, Cat-B and Cat-C were synthesized. Cat-A was synthesized without any internal Lewis base (ILB); while Cat-B and Cat-C were synthesized using diisobutyl phthalate and ethyl benzoate as ILBs respectively. The effect of ILBs on stereoregularity and the microstructure of polybutadiene (PBD) was investigated. The vast differences in the amount of trans-1,4-structure of PBD by Cat-A, Cat-B and Cat-C systems were correlated with the nature of ILBs used by studying their polymerization kinetics. The energy barriers for polymerization reactions were calculated for all three catalysts systems using Arrhenius equation. Cat-B, has shown the highest energy barrier (23 kJ/mol) due to DIBP as ILB in its structure. Cat-A has given the lowest trans-1,4-PBD as it does not contain any ILB and has the minimum energy barrier (12 kJ/mol) while Cat-C has shown medium energy barrier (17 kJ/mol). We have also studied the effect of suitable external Lewis bases during polymerization. The effect of polymerization parameters like Al/Ti molar ratio, Al/LB molar ratios and the temperatures on PBD microstructure were studied. Based on the polymerization kinetics studies and the effect of LBs on PBD microstructure, a possible reaction mechanism has been proposed.

Anionic polymerization of butadiene by dialkylmagnesium / alkali metal alkoxide systems in apolar medium: Polybutadiene microstructure and polymerization control

Lithium based anionic polymerization of butadiene in apolar media allows the obtention of polybutadiene with a high vinyl content by using polar modifier or alkali metal alkoxide. For instance, butadiene polymerization with alkyllithium and potassium tert-pentoxide produces polybutadiene with 50% of vinyl content. The aim of this paper is to develop an approach without any alkyllithium moieties in order to synthesize polybutadiene with a high vinyl content (50%–70%) in a controlled way. To do so bi-metallic systems based on di-n-butylmagnesium in association with potassium or sodium tert-pentoxide were studied in apolar medium. The influence of parameters such as the initiator preformation time and the [Mt]/[Mg] ratio were assessed (Mt = K, Na). The potassium tert-pentoxide-based system was found to produce polybutadienes in a controlled way with 50% of vinyl content, while polybutadienes with up to 70% of vinyl content were obtained in a controlled way with Na based systems.

Anionic Polymerization of Butadiene Using Lithium/Potassium Multi-metallic Systems: Influence on Polymerization Control and Polybutadiene Microstructure

Thermal, mechanical, and viscoelastic properties of polybutadiene-based rubber materials are highly dependent on polybutadiene microstructure. The use of polar modifier in association with alkyllithium is a well-known method to obtain polybutadiene with a high vinyl content. Another approach is to use bimetallic initiating species such as alkyllithium combined to heavier alkali metal alkoxide (RONa, ROK…). The polymerization control is nevertheless not achieved and several parameters were found to influence it. Using bimetallic initiating systems based on alkyllithium and a potassium alkoxide, alkyllithium structure, initiator preformation time, and initiator composition were identified as parameters influencing the anionic polymerization process of butadiene and/or polybutadiene microstructure. In addition, the use of trimetallic systems based on alkyllithium, potassium alkoxide, and alkylaluminum was investigated in order to prevent side reactions regardless of the [K]/[Li] ratio and of the initiator preformation time.

Accessible microstructures of polybutadiene by anionic polymerization

Mechanical and viscoelastic properties of polybutadiene-based rubber materials are highly dependent on polybutadiene microstructure along with molar mass, dispersity, polymer architecture and styrene content for copolymers. In addition, the living character of anionic polymerization of butadiene allows the precise chain-end functionalization and synthesis of block copolymers. Knowing that mainly the nature of the counter-ion or solvents influence strongly the polybutadiene microstructure, a summary of all anionic or related strategies is proposed in this review to tune polybutadiene microstructures. The influence of alkali metals, alkaline earth metals and multi-metallic compounds as well as their environment is discussed.

Structural characterization of polybutadiene synthesized via cationic mechanism

ABSTRACTThe microstructure of polybutadiene synthesized via cationic polymerization using TiCl4‐based initiating systems has been investigated using 1D (1Н, 2Н, and 13С) and 2D (HSQC and HMBC) NMR spectroscopy. It was found that trans‐1,4‐unit is predominant structure of unsaturated part of polymer chain. Besides, the small amount of 1,2‐structures was also detected, while cis‐1,4‐units were totally absent. The signals of carbon atoms of three types of head groups (trans‐1,4‐, 1,2‐, and tert‐butyl) and two types of end groups (trans‐1,4‐Cl and 1,2‐Cl) were identified for the first time in macromolecules of cationic polybutadiene. It was showed that tert‐butyl head groups were formed due to the presence in monomer of admixtures of isobutylene. The new methodology for calculation of the content of different structural units in polybutadiene chain as well as the head and end groups was proposed. It was established that main part of 1,2‐units distributed randomly along the polybutadiene chain as separate units between trans‐1,4‐structures. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 387–398

Effect of enthalpy of polar modifiers interaction with n-butyllithium on the reaction enthalpy, kinetics and chain microstructure during anionic polymerization of 1,3-butadiene

The influence of interaction enthalpy (ΔHMOD/BuLi) of μ, σ, σ+μ and σ-μ complexing polar modifiers with n-butyllithium on the 1,3-butadiene anionic polymerization enthalpy (ΔHBD), polymerization reaction rate (kp) and polybutadiene microstructure was studied. It has been found that enthalpy of interaction depends on complex type, molar ratio of polar modifier to n-butyllithium (MOD/BuLi) and temperature. For the first time it has been proven that with increasing ΔHMOD/BuLi the content of 1,2 butadiene (vinyl) units in the chain increases individually for each complex type but the value of ΔHBD decreases similarly for all complexes containing σ-donor groups, exhibiting linear nature. Since ΔHMOD/BuLi controls the content of butadiene isomeric structures in the chain its value was compared with polymerization reaction rate, ranging from ∼46 to ∼5500 moL/L·min, and discussed on mechanistic level.

EFFECT OF STEREOCHEMISTRY IN ANIONIC POLYMERIZATION MODIFIERS

ABSTRACT The influence of stereochemistry of polar modifiers on the microstructure of polybutadiene and poly(styrene-co-butadiene) was evaluated for 2,2′-ditetrahydrofurylpropane (DTHFP). The meso and d,l diastereomers were isolated from commercial 50/50 mixtures through column chromatography and characterized by 1H-NMR and gas chromatography/mass spectrometry. The meso-DTHFP was found to be more active than d,l-DTHFP in incorporation of vinyl during anionic polymerization. To form a polymer with approximately 55% vinyl, twice the amount of d,l-DTHFP was required compared with using pure meso-DTHFP. The mechanism for this effect will be discussed.

Influence of polar modifiers on microstructure of polybutadiene obtained by anionic polymerization. Part 5: Comparison of µ, σ, σ+µ, and σ−µ complexes

ABSTRACTA comparison was performed of the influence of polar modifiers forming (separately or simultaneously) σ and μ complexes with a living center during anionic polymerization of 1,3-butadiene — regarding the content and distribution of butadiene isomeric structures. Analysis of the 1H NMR, 13C NMR, and FT-IR data indicated a significant discrepancy in terms of the determination of the polybutadiene microstructure depending on the analytical method applied. Nevertheless, it was observed that the application of polar modifiers forming different types of complexes with organometallic compounds provided the possibility to govern the content of 1,4- and 1,2-butadiene units in a very broad range (0.55 < cis/trans < 1.05 and 10% < vinyl < 90%, respectively) as well as to control diad distribution.

Comprehensive Microstructure and Molar Mass Analysis of Polybutadiene by Multidimensional Liquid Chromatography.

For the first time, polybutadiene is separated according to microstructure using solvent gradient interaction chromatography (SGIC). Superior separation of polybutadienes having different microstructures is obtained on a silica-based reversed stationary phase and a mobile phase of acetone-hexane. This SGIC system enables the baseline separation of 1,2-polybutadienes and 1,4-polybutadienes even in cases where the samples have similar molar masses. 2D liquid chromatography is performed with the SGIC method separating according to microstructure in the first dimension coupled to size exclusion chromatography separating according to molar mass in the second dimension, thus providing comprehensive information on both microstructure and molar mass.

Influence of polar modifiers on microstructure of polybutadiene obtained by anionic polymerization. Part 4: Acid-base polar modifiers forming σ-μ complexes: Amine-alkoxide, amine-ether-alkoxide, and ether-alkoxide

ABSTRACTThe influence of acid-base polar modifiers (σ-μ complex): amine-alkoxide, amine-ether-alkoxide, and ether-alkoxide complexes on microstructure of polybutadiene obtained by anionic polymerization was studied. The content of butadiene isomeric structures was determined based on FT-IR-ATR, 1H, and 13C NMR data analyses. The results obtained indicated a very similar influence of all types of polar modifiers forming σ-μ complex on polymer microstructure leading to high vinyl polybutadiene with nearly equal ratios of cis-1,4 and trans-1,4 butadiene isomeric structures.

Influence of polar modifiers on microstructure of polybutadiene obtained by anionic polymerization. Part 3: Lewis acid alkoxide (μ) and Lewis base amine, amine-ether, and ether mixed-type (σ+μ) polar modifiers

ABSTRACTThe influence of mixtures of sodium mentholate (SMT) as a Lewis acid polar modifier and different Lewis base polar modifiers (amines, amine-ethers, ethers) on the microstructure of polybutadiene obtained by anionic polymerization was studied and compared to the influence of the same polar modifiers used separately. Detailed characterization of the polybutadienes in terms of the content and distribution of butadiene isomeric repeating units was performed by 13C NMR and supported by FT-IR-ATR and 1H NMR data analysis. The results obtained indicated that the use of a mixture of Lewis acid and Lewis base in most cases enhanced formation of 1,2 butadiene structures in comparison to the Lewis bases used separately. However, application of a mixture of SMT and DTP resulted in lower vinyl content than when DTP was applied alone. It is worthwhile to note that the combination of a Lewis acid (SMT) and one of Lewis bases tested (DMEAEE) enabled obtaining very high vinyl polybutadiene (88% 1H NMR, 96% 13C NMR).

Influence of Polar Modifiers on Microstructure of Polybutadiene Obtained by Anionic Polymerization. Part 2: Lewis Base (σ) Amine-Ether and Ether-Type Polar Modifiers

The influence of Lewis base (σ complex) amine-ether and ether-type polar modifiers on the microstructure of polybutadiene obtained by anionic polymerization was studied. Analysis of FT-IR-ATR, 1H, and 13C NMR spectral data for polybutadienes obtained in the presence of the complexing agents showed that increase of concentration of all tested polar modifiers very strongly promoted formation of 1,2 butadiene isomeric structures, especially increasing the content of vinyl–vinyl and vinyl–trans-1,4 diads.

Influence of Polar Modifiers on Microstructure of Polybutadiene Obtained by Anionic Polymerization. Part 1: Lewis Base (σ) Amine-Type Polar Modifiers

In order to understand the influence of various types of polar modifiers on the microstructure of polybutadiene obtained by anionic polymerization, four types of polar modifiers were selected for detailed studies: Lewis bases (σ complex), Lewis acids (μ complex), a mixture of Lewis bases and Lewis acids (σ + μ complex), and acid-base polar modifiers (σ-μ complex) where one molecule combined acid and base character. The influence of five different tertiary amines (Lewis base polar modifiers) was studied. Analysis of FT-IR-ATR, 1H, and 13C NMR data for polybutadienes obtained in the presence of these complexing agents showed that all tested tertiary amines enhanced 1,2 addition of 1,3-butadiene and preferred trans-1,4 addition.

Avaliação das razões molares Cl:Nd e Al:Nd na polimerização de 1,3-butadieno com o sistema catalítico versatato de neodímio/hidreto de di-isobutilalumínio/cloreto de t-butila

O objetivo deste trabalho foi estudar sistemas cataliticos ternarios constituidos por versatato de neodimio, cloreto de t-butila e hidreto de di-isobutil-aluminio para a polimerizacao de 1,4-cis de butadieno em hexano. Foram investigados os efeitos das razoes molares Cl/Nd e Al/Nd sobre a reacao de polimerizacao. Os polimeros foram caracterizados por cromatografia de exclusao por tamanho (SEC), espectroscopia na regiao do infravermelho (FT-IR) e viscosimetria no estado fundido. A atividade catalitica, massa molar, distribuicao de massa molar e viscosidade Mooney foram fortemente influenciados pela variacao da razao molar Cl/Nd. Os maiores teores de unidades cis foram observados em razoes molares Cl/Nd > 3. O valor maximo de atividade catalitica foi obtido em razoes molares Cl/Nd na faixa de 3 a 5. A microestrutura do polibutadieno foi significativamente influenciada pelo aumento da razao molar Al/Nd. Foi observado um valor maximo, 99% de unidades cis, na razao molar Al/Nd = 10. Os dados de conversao versus tempo de reacao mostraram que a velocidade de polimerizacao aumenta com a razao molar Al/Nd alcancando um valor maximo na razao molar Al/Nd=23. As curvas de distribuicao de massa molar evidenciaram um significativo processo de transferencia de cadeia para os polimeros produzidos em razoes Al/Nd mais altas.

Deformation and orientation behavior of polystyrene-b-polybutadiene-b-poly(methyl methacrylate) triblock terpolymers: Influence of polybutadiene microstructures and the molar masses

Morphological changes caused by deformation and orientation of different domains of polystyrene-b-polybutadiene-b-poly(methyl methacrylate), SBM, triblock terpolymers were investigated using in-situ small angle X-ray scattering (SAXS), tensile testing, and transmission electron microscopy (TEM). Two sets of SBM triblock terpolymers with similar weight fractions of the three blocks were studied. The two sets differ in terms of their molecular weights. Each set contained two SBM differing in their polybutadiene isomers (1,2- and 1,4-B). Results showed that for 1,2-B based SBMs the polybutadiene block forms cylindrical domains which coalesce in the glassy lamellar matrix of the two glassy outer blocks whereas the lower molar mass 1,4-B based SBM forms mixed S/M and the higher one forms well segregated long range ordered lamellae. These morphological differences indicate that the deformation and the orientation behavior of the polymers' domains differ. In 1,2-B based SBMs yielding at high stresses was followed by a stress drop after the yield point. The other polymer type showed homogeneous deformation of the lamellar domains at their yield point. 2D-SAXS during deformation of the triblock terpolymers showed an anisotropic deformation pattern in the 1,2-B SBMs, whereas four point SAXS patterns were found for the 1,4-B SBMs. Further studies showed that the fragmented lamellar planes of the lower molar mass 1,2-SBM oriented randomly whereas the orientation of the lamellar planes of the higher molar mass 1,2-B SBM was parallel to the strain direction. The alignment of the lamellar planes of 1,4-B SBMs were randomly distributed in the unstretched state.

Influence of (1,3‐phenylene)bis(3‐methyl‐1‐phenyl pentylidene)dilithium initiator concentration on the modality of polybutadiene

AbstractThe strong influence of (1,3‐phenylene)bis(3‐methyl‐1‐phenyl pentylidene)dilithium initiator (DLI) concentration on the modality of polybutadiene (PBd) in the presence of lithium s‐butoxide (s‐BuOLi) in benzene, at room temperature, has been studied. The quality of DLI has been evaluated by gas chromatography‐mass spectrometry (GC‐MS) and 1H NMR. Keeping s‐BuOLi/C‐Li ratio (R) close to unity, at relatively high DLI concentrations (C &gt; 7 × 10−4 M), monomodal high 1,4‐PBds with polydispersity index less than 1.07 were obtained, whereas bimodal ones at lower concentrations (C &lt; 6 × 10−4 M). The effect of C‐Li concentration on the modality of PBd has been evaluated using size exclusion chromatography on samples taken during and at the end of the polymerization. Viscosity observations have also been used to further support the results. The bimodality of PBd has been attributed to partially terminated difunctional species because of the inevitable presence of protic impurities in the polymerization solution, although high vacuum technique was used, which becomes more significant at low initiator concentrations. Moreover, the strong influence of s‐BuOLi on the microstructure of PBd has been demonstrated by 1H NMR. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013

Synthesis of random or tapered solution styrene–butadiene copolymers in the presence of sodium dodecylbenzene sulfonate as a polar modifier

AbstractRandom or tapered solution styrene–butadiene copolymer (SSBR) is very difficult to prepare in an isothermal batch process without the use of polar modifiers because of the diverse reactivity ratios of the styrene and the butadiene in hydrocarbon solvents. In the presence of polar modifiers, the random SSBR can be synthesized by anionic living polymerization with the variety of microstructures, which results in the change of glass transition temperature (Tg). This article will discuss the use of sodium dodecylbenzene sulfonate as a polar modifier in isothermal batch process that controls the microstructure of the SSBR resulting in a random as well as tapered SSBR with low Tg (−67°C to −80°C). The Tg of SSBR was controlled by the styrene content rather than the microstructure of polybutadiene. Physical properties of SSBR compounding were discussed for tire tread applications. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Mechanisms for anionic butadiene polymerization with alkyl lithium species

Anionic butadiene polymerization by means of [Li-polybutadienyl]x species (x = 1–6, 8) without polar agents was investigated by means of density functional theory (DFT) under conditions relevant to industrial application, namely in a low-dielectric hydrocarbon solvent and at room temperature. The calculations indicate that the dimeric and tetrameric catalyst species together account for the bulk of Li-polybutadienyl species in the polymerization mixture under typical conditions. It is likely that each type of oligomer produces its own “fingerprint” signature polymer microstructure, as there is a systematic variation in the amounts of 1,2- and 1,4-insertions as well as in the preference of cis- and trans-butadiene. According to the calculations, higher aggregated Li species tend to produce more 1,2-insertions and prefer trans- over cis-butadiene insertion, while the dimer prefers trans-butadiene and 1,4-insertions. The dimer closely reproduces the experimentally observed polybutadiene microstructure (5%–10% 1,2-insertion, approximately equal ratios of cis and trans units with a slight predominance of trans). The monomeric catalyst species shows a clear preference for insertion of cis-butadiene over trans-butadiene. Thus, the monomer species is predicted to be present in the polymerization mixture in very small concentrations under normal conditions and the overall polymerization is predicted to be mainly carried out by the dimeric catalyst species.

Changes in the microstructure and morphology of high-impact polystyrene subjected to multiple processing and thermo-oxidative degradation

Multiple processing and thermo-oxidation have been employed to simulate the degradative processes to which high-impact polystyrene (HIPS) is subjected during processing, service life, and mechanical recycling. A curve-fitting procedure has been proposed for the analysis of the individual bands corresponding to polybutadiene microstructure resulting from Raman spectroscopy. The analysis of the glass transition relaxations associated with the polybutadiene (PB) and polystyrene (PS) phases has been performed according to the free-volume theory. Both reprocessing and thermo-oxidative degradation are responsible for complex physical and chemical effects on the microstructure and morphology of PB and polystyrene PS phases, which ultimately affect the macroscopic performance of HIPS. Multiple processing affects PB microstructure and the free-volume parameter associated with the PS phase. Physical ageing of the PS phase predominates for shorter exposure to thermo-oxidation; after prolonged exposure, however, the chemical effects on the PB phase become significant and strongly influence the overall structure.