Range Of Copolymer Composition Research Articles

Challenging Isodimorphism Concepts: Formation of Three Crystalline Phases in Poly(hexamethylene-ran-octamethylene carbonate) Copolymers.

In this work, poly(hexamethylene-ran-octamethylene carbonate) copolycarbonates were synthesized by melt polycondensation in a wide range of compositions. The copolymers displayed some of the characteristic isodimorphic thermal behavior, such as crystallization for all the compositions and a pseudoeutectic behavior of the melting temperature (Tm) versus composition. The pseudoeutectic point was located at 33 mol % poly(octamethylene carbonate) (POC) content (i.e., corresponding to the PH67O33C copolymer). Surprisingly, the crystallinities (Xc) for a wide range of copolymer compositions were higher than those of the parent components, a phenomenon that has not been observed before in isodimorphic random copolymers. The structural characterization, performed by wide-angle X-ray scattering (WAXS) and small-angle X-ray scattering experiments, revealed unexpected results depending on composition. On the one hand, the poly(hexamethylene carbonate) (PHC)- and POC-rich copolymers crystallize in PHC- and POC-type crystals, as expected. Moreover, upon cooling and heating, in situ WAXS experiments evidenced that these materials undergo reversible solid-solid transitions [δ-α (PHC) and δ-α-β (POC)] present in the parent components but at lower temperatures. On the other hand, a novel behavior was found for copolymers with 33-73 mol % POC (including the pseudoeutectic point), which are those with higher crystallinities than the parent components. For these copolymers, a new crystalline phase that is different from that of both homopolymers was observed. The in situ WAXS results for these copolymers confirmed that this novel phase is stable upon cooling and heating and does not show any crystallographic feature of the parent components or their solid-solid transitions. FTIR experiments confirmed this behavior, revealing that the new phase adopts a polyethylene-like chain conformation that differs from the trans-dominant ones exhibited by the parent components. This finding challenges the established concepts of isodimorphism and questions whether a combination of crystallization modes (isodimorphism and isomorphism) is possible in the same family of random copolymers just by changing the composition.

Synthesis and properties of surfactants for carbon nanotubes based on copolymers of 2-N-morpholinoethyl methacrylate with dodecyl methacrylate and styrene

The copolymerization reactivity ratios for 2-N-morpholinoethyl methacrylate (MEMA) with dodecyl methacrylate (DDMA) or styrene (ST) were estimated. The efficiency of the prepared polymers for dispersion of MWCNT in toluene was also studied. A wide range of copolymer compositions (all 10 mol% steps) were prepared using tert-butyl peroxy-2-ethylhexanoate (0.02 mol dm−3) as initiator isothermally (70 °C) to low conversions (< 10 wt%). In the case of DDMA/MEMA copolymerization, there is a slight tendency for both monomers to react more with MEMA. The reactivity ratios obtained are r(DDMA) = 0.86 and r(MEMA) = 1.05. The reactivity ratios for the copolymerization of ST/MEMA are both <1 and are r(ST) = 0.35 and r(MEMA) = 0.59, indicating a higher reactivity of each monomer with the other monomer. The addition of small amounts (10 mol%) of MEMA to DDMA homopolymer significantly increases its thermal stability (the temperature at 50 wt% loss is 46 °C higher). For ST/MEMA, the addition of MEMA gradually decreases the thermal stability (the temperature difference at 50 wt% loss between the homopolymers is 25 °C). The best dispersion of MWCNT in toluene is obtained with the ST/MEMA copolymer containing 42 mol% MEMA, as shown by UV–Vis measurements and visual inspections after the gravity test. The obtained results contribute to the further development of polymeric surfactants and stimuli-responsive polymers.

Reversible Addition-Fragmentation Chain Transfer Aqueous Dispersion Polymerization of 4-Hydroxybutyl Acrylate Produces Highly Thermoresponsive Diblock Copolymer Nano-Objects.

The reversible addition-fragmentation chain transfer (RAFT) aqueous dispersion polymerization of 2-hydroxypropyl methacrylate (HPMA) using a poly(glycerol monomethacrylate) (PGMA) precursor is an important prototypical example of polymerization-induced self-assembly. 4-Hydroxybutyl acrylate (HBA) is a structural isomer of HPMA, but the former monomer exhibits appreciably higher aqueous solubility. For the two corresponding homopolymers, PHBA is more weakly hydrophobic than PHPMA. Moreover, PHBA has a significantly lower glass transition temperature (Tg) so it exhibits much higher chain mobility than PHPMA at around ambient temperature. In view of these striking differences, we have examined the RAFT aqueous dispersion polymerization of HBA using a PGMA precursor with the aim of producing a series of PGMA57–300-PHBA100–1580 diblock copolymer nano-objects by systematic variation of the mean degree of polymerization of each block. A pseudo-phase diagram is constructed using transmission electron microscopy to assign the copolymer morphology after employing glutaraldehyde to cross-link the PHBA chains and hence prevent film formation during grid preparation. The thermoresponsive character of the as-synthesized linear nano-objects is explored using dynamic light scattering and temperature-dependent rheological measurements. Comparison with the analogous PGMAx-PHPMAy formulation is made where appropriate. In particular, we demonstrate that replacing the structure-directing PHPMA block with PHBA leads to significantly greater thermoresponsive behavior over a much wider range of diblock copolymer compositions. Given that PGMA-PHPMA worm gels can induce stasis in human stem cells (see Canton et al., ACS Central Science, 2016, 2, 65–74), our findings are likely to have implications for the design of next-generation PGMA-PHBA worm gels for cell biology applications.

Tuning the Properties of Biodegradable Poly(Butylene Succinate) Via Random and Block Copolymerization

In this mini-review, the effect of random and block copolymerization on crystallization and properties of biodegradable poly(butylene succinate) is outlined. For random copolymerization, the effect of minor co-monomers can be divided into two categories: In most of the cases, the minor co-monomer units will be excluded from the crystal lattice of the major monomer units, which leads to the decreased melting point, lower crystallinity and slower crystallization kinetics. Consequently, the copolymers will be more flexible. Copolymerization with other aliphatic units results in enhanced biodegradation rate, while copolymerization with aromatic units may depress the biodegradation rate. There is an exceptional case, e.g. in poly(butylene succinate-co-butylene fumarate), where the co-monomer units can cocrystallize with the major monomer units in the whole range of copolymer composition, resulting in almost invariant degree of crystallinity. Whether some content of co-monomer units is included in the crystal lattice of the major monomer units or not is still an open question and deserves further study. Furthermore, block copolymerization is an alternative option to tune the properties, which may open a new window for designing biodegradable polymers, especially thermoplastic elastomers. Block and multiblock copolymers combine the properties of the different blocks and the crystallization behavior depends on the block length and miscibility of the blocks. When the block length is large enough, the melting point of such block will not vary much with its content, which is distinctly different from the random copolymers. Incorporation of more hydrophilic blocks, such as aliphatic polyethers will considerably enhance the hydrolytic degradation rate.

Superswelling of Hydrogels Based on the Copolymer of Acrylamide and Methacrylic Acid

Weakly crosslinked hydrogels of copolymers of acrylamide and methacrylic acid are synthesized by radical polymerization in aqueous solution in a wide range of comonomer ratios. It is found that gels containing 20–40 mol % methacrylic acid are characterized by superswelling that exceeds the degree of swelling of homopolymer hydrogels by tens of times. The observed degree of swelling reaches 830, corresponding to an almost completely stretched conformation of subchains between network junctions. For dried hydrogel samples, the equilibrium degree of swelling is also maximal in the mentioned composition range; however, its maximum value is lower than the equilibrium degree of swelling for the initial samples. The possible reason behind the superswelling of hydrogels containing 20–40% units of methacrylic acid is an increase in ionization of network subchains. This hypothesis is proved by an increased sensibility of hydrogels of this composition to a change in the pH of a medium and the lowest values of the effective acidity constant determined by potentiometric titration for methacrylic acid units. The values of partial heat capacity of a gel polymer network are determined by calorimetry. These values are significantly higher than the heat capacities typical of vinyl polymers. This is evidence that the hydrophobic type of hydration predominates in the copolymers of acrylamide and methacrylic acid. The partial heat capacity reaches its maximum within the copolymer composition range corresponding to superswelling.

Phase Behavior of Mixtures of Block Copolymers and a Lithium Salt

We present experimental results on the phase behavior of block copolymer/salt mixtures over a wide range of copolymer compositions, molecular weights, and salt concentrations. The experimental system comprises polystyrene- block-poly(ethylene oxide) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt. It is well established that LiTFSI interacts favorably with poly(ethylene oxide) relative to polystyrene. The relationship between chain length and copolymer composition at fixed temperature is U-shaped, as seen in experiments on conventional block copolymers and as anticipated from the standard self-consistent field theory (SCFT) of block copolymer melts. The phase behavior can be explained in terms of an effective Flory-Huggins interaction parameter between the polystyrene monomers and poly(ethylene oxide) monomers complexed with the salt, χeff, which increases linearly with salt concentration. The phase behavior of salt-containing block copolymers, plotted on a segregation strength versus copolymer composition plot, is similar to that of conventional (uncharged) block copolymer melts, when the parameter χeff replaces χ in segregation strength.

Estimating and Comparing the Electrical Properties of a Homologous Series of Polyethylene Carbonate and Polyester Copolymer Electrolytes

A pseudo-chemical equilibrium model has been used to estimate and compare the glass-transition temperatures and ionic conductivities of solid polymer electrolytes (SPEs) made with amorphous aliphatic ether-containing polyethylene carbonate and polyester copolymers. Model parameters were estimated using experimental data from prior studies for three polyethylene carbonate and three polyester copolymer SPEs and then extended to other SPEs within each homologous series. The estimated properties are compared and generally agree with available published experimental data over a range of copolymer compositions with LiFSI and LiTFSI. Simple models using available data for the lithium ion transference number of the polyethylene carbonate copolymer SPEs also were developed. Results from the models are used to estimate and compare the balance of electrical properties for this range SPEs with poly(ethylene oxide) with LiTFSI at low salt concentrations and with polyethylene carbonate with LiFSI at high salt concentra...

Synthesis, microstructures and properties of amorphous poly(ethylene terephthalate-co- tricyclodecanedimethylene terephthalate)

PET is one of the most important commercial polymers and much effort is being made to modify PET by melt copolymerization with a second glycol or diacid comonomer in a way that yields an amorphous material with a high Tg. In this study, various amounts (0–100 %) of tricyclodecanedimethanol (TCDDM) were used to copolymerize ethylene glycol and terephthalic acid to form a series of copolyesters (PETD). The compositions, microstructures, thermal behaviors, optical transmissions, mechanical properties, and gas transport properties of the copolymers are comprehensively examined over the entire range of copolymer compositions. The experimental results support the tuning of the properties of these copolymers by adjusting their composition. Therefore, they contribute to the design of new PET materials with a better balance among thermal, mechanical, optical, and gas transport properties.

Reactivity ratios and properties of copolymers of 2-ethoxyethyl methacrylate with dodecyl methacrylate or styrene

The copolymerization reactivity ratios for 2-ethoxyethyl methacrylate (EOEMA) with dodecyl methacrylate (DDMA) or styrene (ST) were estimated. Polymerization was performed by using tert-butyl peroxy-2-ethylhexanoate (0.01 mol dm−3) as initiator, isothermally (70 °C) to low conversions (< 10 wt.%) in a wide range of copolymer compositions (every 10 mol-% steps). For the DDMA/EOEMA copolymerization both monomers prefer to react with EOEMA: r (DDMA) = 0.82 and r (EOEMA) = 1.26 with r (DDMA) × r (EOEMA) = 1, which results in the random copolymerization. For the ST/EOEMA copolymerization reactivity ratios are r (ST) = 0.59 and r (EOEMA) = 0.49 indicating a higher reactivity with opposite monomer, while the alternation tendency is not highly pronounced. The probabilities for formations of dyad and triad monomer sequences in dependence on monomer compositions were calculated from the obtained reactivity ratios. With the share increase of ST or DDMA in copolymers surface properties changed from hydrophilic to hydrophobic. Glass transition temperature of copolymer increased with the increase of ST and decrease of DDMA. The molar mass distribution and thermal degradation of synthesized copolymers were also determined and discussed. The reactivity ratios enable optimization of copolymer properties for a given application as polyelectrolytes, drug delivery systems and multifunctional additives for improvement of rheological properties of lubricating oils.

Reactivity ratios and copolymer properties of 2‐(diisopropylamino)ethyl methacrylate with methyl methacrylate and styrene

AbstractFree radical copolymerization kinetics of 2‐(diisopropylamino)ethyl methacrylate (DPA) with styrene (ST) or methyl methacrylate (MMA) was investigated and the corresponding copolymers obtained were characterized. Polymerization was performed using tert‐butylperoxy‐2‐ethylhexanoate (0.01 mol dm−3) as initiator, isothermally (70 °C) to low conversions (&lt;10 wt%) in a wide range of copolymer compositions (10 mol% steps). The reactivity ratios of the monomers were calculated using linear Kelen–Tüdős (KT) and nonlinear Tidwell–Mortimer (TM) methods. The reactivity ratios for MMA/DPA were found to be r1 = 0.99 and r2 = 1.00 (KT), r1 = 0.99 and r2 = 1.03 (TM); for the ST/DPA system r1 = 2.74, r2 = 0.54 (KT) and r1 = 2.48, r2 = 0.49 (TM). It can be concluded that copolymerization of MMA with DPA is ideal while copolymerization of ST with DPA has a small but noticeable tendency for block copolymer building. The probabilities for formations of dyad and triad monomer sequences dependent on monomer compositions were calculated from the obtained reactivity ratios. The molar mass distribution, thermal stability and glass transition temperatures of synthesized copolymers were determined. Hydrophobicity of copolymers depending on the composition was determined using contact angle measurements, decreasing from hydrophobic polystyrene and poly(methyl methacrylate) to hydrophilic DPA. Copolymerization reactivity ratios are crucial for the control of copolymer structural properties and conversion heterogeneity that greatly influence the applications of copolymers as rheology modifiers of lubricating oils or in drug delivery systems. © 2015 Society of Chemical Industry

Ethanolic RAFT Dispersion Polymerization of 2-(Naphthalen-2-yloxy)ethyl Methacrylate and 2-Phenoxyethyl Methacrylate with Poly[2-(dimethylamino)ethyl Methacrylate] Macro-Chain Transfer Agents

The ethanolic reversible addition-fragmentation chain transfer dispersion polymerization (RAFTDP), at 21 wt-%, of 2-(naphthalen-2-yloxy)ethyl methacrylate (NOEMA) and 2-phenoxyethyl methacrylate (POEMA) with a poly[2-(dimethylamino)ethyl methacrylate] macro-chain transfer agent (CTA) with an average degree of polymerization of 20 (PDMAEMA20) is described. DMAEMA20-b-NOEMAy (y = 20–125) block copolymers were readily prepared under dispersion conditions in ethanol at 70°C. However, the polymerization of NOEMA was not well controlled, with size exclusion chromatograms being distinctly bi or multimodal with measured dispersities . Though NOEMA copolymerization was not ideal, the resulting series of block copolymers did exhibit the anticipated full spectrum of nanoparticle morphologies (spheres, worms, and vesicles). Interestingly, these morphology transitions occurred over a relatively narrow range of block copolymer compositions. In the case of POEMA, copolymerization was also poorly controlled with 1.50 ≤ ĐM ≤ 1.83 for the series of DMAEMA20-b-POEMAy copolymers. In contrast to the NOEMA-based copolymers, the POEMA series only yielded nanoparticles with a spherical morphology whose size increased with increasing average degrees of polymerization of the POEMA block. Collectively, though both NOEMA and POEMA can be utilized in ethanolic RAFT dispersion polymerization formulations, these preliminary studies suggest that neither appears to be an ideal aryl methacrylate choice as comonomer, especially if the goal is to combine the synthesis of well-defined copolymers with efficient nanoparticle formation.

Light scattering of ideal random copolymers in bulk

Copolymerization is a useful way of modifying the physical properties of a material to meet specific needs, but it can result in a significant light scattering loss due to dielectric fluctuations in the material. Ideal random copolymers are known to be more transparent; however, the light-scattering properties of such copolymers in bulk have not been fully studied. In this paper, two representative ideal random copolymers were synthesized: methyl methacrylate (MMA)/benzyl methacrylate (BzMA) and MMA/2,2,2-trifluoroethyl methacrylate (TFEMA). The effects of copolymer composition and polymerization temperature on the light-scattering properties were investigated. Polarized light scattering (VV) in copolymers was more sensitive to the polymerization temperature. Higher temperatures were necessary to homogenize the dielectric fluctuations and minimize excess light scattering. However, once the heterogeneous structures vanished, the copolymer bulk exhibited low scattering losses, which are comparable with homopolymers, over the entire range of copolymer compositions.

High Temperature Semibatch Free Radical Copolymerization of Styrene and Butyl Acrylate

AbstractSummary: High temperature semibatch free radical solution copolymerizations of n‐butyl acrylate (BA) and styrene (ST) were carried out over a range of copolymer composition. The significant increase in experimental polymer weight‐average molecular weight with time, as well as the shift in the entire polymer molecular weight distribution, is explained by assuming fast β‐scission of BA midchain radicals with an adjacent styrene unit, followed by subsequent addition of the resultant macromonomer to growing radicals. A mechanistic model including backbiting and β‐scission, macronomer incorporation, long‐chain branching, and propagation and termination penultimate effects was constructed in Predici; the model provides a good representation of the experimental data using rate coefficients taken from literature.

Phase behavior study of poly(N‐tertbutylacrylamide‐co‐acrylamide) in the mixture of water–methanol: The role of polymer–nonsolvent second‐order interactions

AbstractThe phase behavior of poly(N‐tertbutylacrylamide‐co‐acrylamide) (PNTBAM) in pure water and mixture of water–methanol is studied at different temperatures. The different compositions of PNTBAM are prepared by free‐radical polymerization technique and their phase behavior is studied by turbidimetry. The effects of copolymer and solvent composition on the phase behavior of the copolymers are discussed. It has been suggested that the inhomogenities in polymer chains are responsible for lowering the rate of phase transition by increasing the N‐tertbutylacrylamide (NTBAM) and methanol contents in copolymer and mixture, respectively. For the first time we have revealed that there are second‐order binary interactions in the water–methanol which are dominant in the special range of copolymer composition. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 455–462, 2009

Effect of Composition of Substrate-Modifying Random Copolymers on the Orientation of Symmetric and Asymmetric Diblock Copolymer Domains

The ability of random copolymer brushes and cross-linked mats to induce the vertical orientation of domains in overlying films of lamellae- and cylinder-forming block copolymers was investigated as a function of the composition. The substrate-modifying layers consisted of styrene and methyl methacrylate random copolymers and contained either a terminal hydroxyl group or a third polar comonomer of 2-hydroxyethyl methacrylate (HEMA) for grafting brushes to silicon oxide surfaces or glycidyl methacrylate (GMA) for cross-linking the random copolymer into a mat. Polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) lamellae- and cylinder-forming block copolymers (both PS and PMMA minority block copolymers) were deposited and annealed on the modified surfaces. In all cases the vertical orientation of domains was observed for a range of random copolymer composition, but the ranges of composition were different for each combination of surface layer and block copolymer. The cylindrical domains of PS exhibited vertical structures for a very narrow range of compositions compared to cylindrical domains of PMMA or lamellae. As expected, the incorporation of polar HEMA or GMA monomers in the surface layers shifted the composition range for the perpendicular orientation of domains to higher fractions of styrene. The results are discussed in terms of the equilibration of the films in the presence of the chemically modified surfaces.

Synthesis and characterization of amorphous poly(ethylene terephthalate) copolymers containing bis[4-(2-hydroxyethoxy)phenyl]sulfone

Poly(ethylene terephthalate) copolymers (abbreviated as PETS) that contain bis[4-(2-hydroxyethoxy)phenyl]sulfone (BHEPS) were prepared from dimethyl terephthalate (DMT), ethylene glycol (EG) (5–95%) and BHEPS (5–95%). The compositions and microstructures of the copolyesters were determined by 1H and 13C nuclear magnetic resonance (NMR) spectroscopy, respectively. The thermal behaviors were studied over the entire range of copolymer compositions, using X-ray analysis, differential scanning calorimeter (DSC) and thermogravimetric analysis (TGA). The molecular weights, optical characteristics and tensile properties of these polymers were also determined. Experimental results indicated that the copolymers had a random microstructure. The intrinsic viscosities of the copolymers ranged from 0.65 to 0.69 dL/g. The copolyesters with BHEPS of <10 mol% were crystallizable, whereas the copolyesters with BHEPS of ⩾10 mol% were amorphous. Incorporating BHEPS affected the glass-transition temperature ( T g) values of those polymers, from about 81 °C for PETS 5 to 126 °C for PETS 95. The optical transmissions exceeded 86% for λ = 400 nm for all of the amorphous polyesters. The tensile modulus and strength of the copolyesters increased with BHEPS. However, they also became brittle and their elongation at break decreased.

Amorphous copolyesters based on 1,3/1,4‐cyclohexanedimethanol: Synthesis, characterization and properties

AbstractTwo series of amorphous copolyesters, PETGN and PETGS, were synthesized by the copolymerization of 2,6‐naphthalene dicarboxylic acid (NDA) (0–40%), succinic acid (SA) (0–40%), 1,3/1,4‐cyclohexanedimethanol (1,3/1,4‐CHDM) (10–50%), ethylene glycol (EG), and terephthalic acid (TPA). The compositions and molecular weights of the copolyesters were determined by 1H NMR spectroscopy and viscometry, respectively. The thermal behaviors were studied over the entire range of copolymer compositions, using DSC and TGA. The optical characteristics, heat‐shrinkable effects and tensile properties of these polymers were also determined. Experimental results indicated that the thermal, optical, tensile, and shrinkage properties of PETGN and PETGS were functions of NDA or SA content. DSC and X‐ray analysis demonstrated that both PETGN and PETGS series were amorphous. Incorporating NDA and SA influenced the Tg values of those polymers, from about 37°C for PETG30S40 to 89°C for PETG30N40. Furthermore, the shrinkage of these amorphous copolyesters was more than 40% when the heating temperature was higher than the corresponding Tg. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Broad ultraviolet protection by copolymerization of 2‐[3‐(2H‐benzotriazol‐2‐yl)‐4‐hydroxyphenyl]ethyl methacrylate and 2‐hydroxy‐4‐acryloyloxybenzophenone on cotton via admicellar polymerization

AbstractTwo monomers with complimentary ultraviolet absorbing moieties, 2‐[3‐(2H‐benzotriazol‐2‐yl)‐4‐hydroxyphenyl]ethyl methacrylate (BEM) and 2‐hydroxy‐4‐acryloyloxybenzo phenone (HAB), were copolymerized through admicellar polymerization on a cotton fabric surface in order to improve its ultraviolet protection with broad spectral coverage. Separate and combined adsolubilization of the two monomers in dodecylbenzenesulfonate admicelles were studied and compared. Copolymer composition and monomer reactivity ratio were investigated by FTIR using Fineman–Ross and Kelen–Tüdos methods and it was found that the BEM‐HAB copolymer system showed an alternating tendency and exhibited azeotropic polymerization at a particular composition. The copolymerization method used in this study provided a cotton fabric with uniform and complete UV‐protection in the most hazardous regions. Ultraviolet protection factor (UPF) of the modified cotton was studied with a range of copolymer compositions and it was found that the fabrics coated by copolymer had higher values of UPF than homopolymers, while the monomer ratio of 1 : 1 gave the highest UPF value. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008

Synthesis of propylene/1-butene copolymers in liquid pool and gas-phase processes: A comparative analysis

Batch liquid pool and semibatch gas-phase polymerizations were performed with high-activity Ziegler–Natta catalysts to evaluate the effect of 1-butene on the crystallinity, the melt temperature and the average molecular weights of the final 1-butene/propylene copolymers and alloys. According to the obtained results, 1-butene can be significantly incorporated into the polymer chain over the whole range of copolymer compositions in both gas and liquid-phases, leading to the decrease of the melting temperature of the copolymer resins. On the other hand, the properties of the polymer alloys seem to be less sensitive to 1-butene incorporation, indicating the development of a distinct 1-butene phase. The average molecular weights, the polydispersities and the reactivity ratios are quite different in the liquid pool and gas-phase processes, indicating that sorption/ diffusion effects may exert an important role during the copolymerization. The obtained reactivity ratios in the gas-phase are close to 1, while the reactivity ratios of propylene are systematically higher than the reactivity ratios of 1-butene in the liquid pool process. Polymer materials with large molecular weights and good particle morphology can be obtained in all analyzed cases, indicating that development of propylene/1-butene copolymer grades is indeed possible in both liquid pool and gas-phase processes.

Synthesis and mesophase behaviors of 2,5-disubstituted styrene-based random copolymers: Effect of difference in side-group length on liquid crystallinity

Five series of binary copolymers, poly[2,5-di(ROOC)styrene- co-2,5-di(R′OOC)styrene]s (R = n-C 3H 7–, R′ = C 2H 5–, n-C 4H 9–, and n-C 5H 11–; R = n-C 6H 13–, R′ = n-C 4H 9–, and n-C 5H 11–), were synthesized via free radical polymerization. The random nature of the copolymers was expected on the basis of the assumed similar reactivities of the analogous monomers and proved by 13C NMR analysis. It was also implied by the smoothly varying glass transition temperatures and further supported by the monotonous variation in d spacings for the liquid crystalline copolymers, where both corresponding homopolymers are liquid crystals. Subtle difference of R and R′ was found to have significant impact on the mesomorphic properties of the copolymers. When the pair of the corresponding homopolymers has the same mesogenic structure, a difference of one carbon atom in the alkyl chain can be tolerated over the whole copolymer composition range; however, the liquid crystalline structure soon disappears with the incorporation of a co-unit of an homopolymer that is not liquid crystal. For the copolymers with alkyl chain length differing by two carbon atoms, the liquid crystalline structure is lost with the incorporation of relatively low co-unit content despite the pair of corresponding homopolymers having the same mesogenic structure.