High Polymerization Temperature Research Articles

Photo-induced surface grafting of phosphorylcholine containing copolymers onto mesoporous silica nanoparticles for controlled drug delivery

Surface modification of mesoporous silica nanoparticles (MSNs) with functional polymers has become one of the most interest topics over the last decade. Among various surface modification strategies, surface-initiated atom transfer radical polymerization (ATRP) has been regarded as one of the most effective methods. However, the typical ATRP strategy is relied on the transition metal ions and their organic ligands as the polymerization catalyst systems. In this work, a novel surface-initiated ATRP method was established for surface functionalization of MSNs using 10-Phenylphenothiazine (PTH) as the catalyst, 2-methacryloyloxyethyl phosphorylcholine (MPC) and itaconic acid (IA) as the monomers. We demonstrated that photo-induced ATRP is very effective for preparation of polymer functionalized MSNs (MSNs-NH2-poly(IA-co-MPC)). More importantly, MSNs-NH2-poly(IA-co-MPC) displayed well water dispersity, low cytotoxicity, high loading capability and controlled release behavior towards cisplatin. Furthermore, the method based on photo-induced surface-initiated ATRP could effectively overcome the drawbacks of conventional ATRP, which may involve in the residue of transition metal ions, high polymerization temperature, long polymerization term and complex experimental procedure. Therefore, this strategy described above is of great interest for fabrication of multifunctional polymer composites for various applications.

Excellent Control of Perylene Diimide End Group in Polyfluorene via Suzuki Catalyst Transfer Polymerization

Six aryl Pd(II) bromide complexes based on perylene diimide derivative (Ar) and phosphine mixed‐ligands are successfully synthesized by directly oxidative addition of Ar–Br to the Pd(0) precursor. These complexes with the general formulas ArPdBr(PCy3)2 (PCy3 = tricyclohexylphosphine; Pd1–Pd3) and [ArPdBr(TXP‐2,4)]2 (TXP‐2,4 = tri‐2,4‐xylylphosphine; Pd4–Pd6) are stable and can be handled in air at room temperature. By employing the Pd(II) complexes as initiators, Suzuki catalyst transfer polymerization (SCTP) of AB‐type fluorene monomer is investigated for preparing polyfluorenes (PFs) with the defined end group. Complexes Pd4–Pd6 with auxiliary TXP‐2,4 ligand can initiate polymerization of AB‐type fluorene monomer at room temperature, while higher polymerization temperature is required for Pd1–Pd3 with alkyl phosphine PCy3. The obtained polymers are analyzed by matrix‐assisted laser desorption ionization‐time‐of‐flight mass spectrometry, which confirms that the Ar group is appended to the terminus of the polymer chain. Moreover, PFs prepared by Pd4–Pd6‐catalyzed SCTP bear precisely the Ar group on one chain end and 4‐tert‐butylphenyl end‐capping group on the opposite end, which indicates that Pd4–Pd6 with the bulky TXP‐2,4 exhibit better catalytic performance in SCTP. Photoluminescence spectra of the obtained polymers show a dual or a blue emission resulting from the difference of the molecular weight. image

Influence of metal softness on the metal-organic catalyzed polymerization of morpholin-2,5-diones to oligodepsipeptides

Synthetic access to oligodepsipeptides (ODP), polymers with high potential in biomedicine, is given by the ring-opening polymerization (ROP) of morpholine-2,5-diones (MDs). Classically, the ROP of MDs is mostly conducted by coordination-insertion polymerization using metal-organics as a catalyst e.g. tin(II) di(2-ethyl hexanoate) (Sn(Oct)2). This ROP has been shown to be significantly more difficult to conduct than the corresponding ROP of dilactide, which was related to different electronic properties of the monomers and potential steric crowding. Here, we investigated the ROP of 3-(S)-sec-butylmorpholine-2,5-dione (BMD) by varying the catalyst’s hardness, comparing Sn(Oct)2 with the ethoxides of indium, magnesium, aluminum and iron(III), as well as with iron(II) acetate. The ROP of BMD with Sn(Oct)2 in bulk at 135°C for 24h gave ODP with a number-average molecular weight (Mn)=4.5kDa. Mg(OEt)2 gave the best results among the other investigated metal ethoxides with ODP of Mn=4kDa and a conversion ratio of 57mol%. On the other hand, high polymerization temperature was needed (160°C) in the case of In(OEt)3, which resulted in partial degradation, while Al(OEt)3 and Fe(OEt)3 did not result in polymerization. Very effective for the ROP of the studied MD proofed to be Fe(OAc)2, giving OBMD with a Mn=5.8kDa, a polydispersity of 1.1, a conversion ratio of 86mol%, and no racemization. This catalyst likewise performed well in the polymerization of Ser- and Tyr-based MDs. Fe(II) is softer than Sn(II) and may support the ROP by promoting the alkoxide transfer step of the polymerization, while suppressing the formation of unreactive coordination complexes. In contrast, the metal alkoxides investigated were harder than Fe(II) or Sn(II), but had low steric demand. The results suggest that the hardness of the central atom is the key property in the polymerization, while steric considerations are of lower importance. In addition, a synthesis of MDs with protected side chains in improved yields was introduced. This was achieved by in situ formation of an alkyl iodide that is very effective in the ring closing reaction.

Acrylic bone cements modified with poly(ethylene glycol)‐based biocompatible phase‐change materials

ABSTRACTThe high polymerization temperature of acrylic bone cements used in hip replacement implantation may cause thermal necrosis of surrounding tissues. In order to reduce the polymerization temperature, acrylic bone cement has been modified with a biocompatible polymeric phase‐change material (PCM) based on poly(ethylene glycol) (PEG) of different molecular weights and stabilized with potato starch. Structural and morphological studies were performed, and the thermal and mechanical properties were investigated. The incorporation of PEG‐based PCM led to a decrease in the polymerization temperature of bone cement from 70 °C for unmodified cement to 58 °C for modified cement. Modified cement materials were stable in incubation tests, although acoustic analysis data revealed a decrease in propagation speed after incubation, which indicates formation of material defects (pores, cracks, voids, etc.) due to water activity. However, in the regeneration process, these defects can be filled by freshly grown bone tissue leading to better incorporation of bone cement replacements into tissue. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43898.

Modification of acrylic bone cements by poly(ethylene glycol) with different molecular weight

The high polymerization temperature of acrylic bone cements can cause arthroplasty failure because of the thermal necrosis of surrounding bone tissue. To reduce this undesired effect we have developed novel acrylic bone cement composites containing a phase change material (PCM). As PCM poly(ethylene glycol) (PEG) of different molecular weight was applied and the effect of its incorporation on curing parameters, mechanical and morphological properties of acrylic bone cement was investigated. A significant decrease in maximum temperature from 65.8°C to 47.4°C and slight increase of setting time were observed. PEG introduction also contributed to the thermal stability of acrylic bone cement increase. SEM investigation of modified bone cement confirmed that the microstructure does not alter considerably because of PEG content. It was found that both PEG addition and incubation test contribute to an inconsiderable decrease in mechanical strength of bone cement. However, the mechanical strength increase can be caused by the fresh bone tissue incorporation into the pores appearing in bone cement. Copyright © 2016 John Wiley & Sons, Ltd.

Copolymerization of 4-methyl-1-pentene with α,ω-alkenols

Copolymerization of 4-methyl-1-pentene (4M1P) with 9-decen-1-ol (9D1O) or 4-penten-1-ol (4P1O) was con- ducted by using metallocene catalysts. The activity could be improved under the higher polymerization temperature. The dyad distribution of poly(4M1P-co-4P1O) was presented. The results showed that 4P1O was uniformly distributed in the copolymer chain. The melting temperature (Tm) of the copolymer was lower than that of poly(4M1P), and was decreased with the increase of the incorporation of comonomer. Tm of poly(4M1P-co-4P1O) was determined as 185 °C, even the in- corporation of 4P1O was high as 15.0 mol%. WAXD (wide-angle X-ray diffraction) results showed that the poly(4M1P) was observed as crystalline form II, and turned to form I when the incorporation of α,ω-alkenols were high. Some new peaks, which were never observed in the previous researches, appeared in the X-ray diffraction profiles for poly(4M1P-co- 4P1O). It is inferred that the similar chain length of 4P1O and 4M1P may be the key factor.

Bifunctional benzoxazines: Synthesis and polymerization of resorcinol based single isomers

ABSTRACTAside from their outstanding properties such as thermal and chemical stability and excellent mechanical performance, benzoxazines suffer from high polymerization temperatures. Isomeric mixtures of bifunctional benzoxazines based on resorcinol proved already to be highly reactive monomers enabling polymerizations at lower temperatures. This contribution describes the polymerization behavior of single benzoxazine isomers and furthermore the influence of different substituents at the aniline moiety on the curing temperature. Single isomers of bifunctional benzoxazines are now accessible in a straightforward one‐pot synthesis starting from resorcinol and the appropriate N‐phenyl functionalized aniline component. The asymmetric benzoxazine monomers bearing no (R‐a: Tpeak = 179 °C) or electron‐donating substituents in meta position to N (R‐3,5dma: Tpeak = 183 °C) succeed in lowering the polymerization temperature. Additionally, the impact of several initiating systems was studied resulting in a decrease of the polymerization temperature for all studied resorcinol derived benzoxazine isomers (down to 144 °C). © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 1243–1251

Microstructure of isotactic polypropylene obtained using Ziegler–Natta catalyst at high polymerization temperature

ABSTRACTThe microstructure of the isotactic polypropylene obtained with various MgCl2‐supported catalyst systems at high polymerization temperature of 70–100°C is investigated by discussing the intrinsic relation between the different types of active centers and the polymerization temperatures via gel permeation chromatography, temperature rising elution fractionation, and 13C NMR. For the MgCl2/TiCl4/di‐n‐butyl phathalate‐AlEt3/external donor and MgCl2/TiCl4/2,2‐diisobutyl‐1,3‐dimethoxypropane‐AlEt3 catalyst systems, the differences in the isotactic productivity of polymers obtained at different polymerization temperatures mainly result from the variation of both the activity of the different isospecific active centers and the stability constants of the complex of catalyst/donor. The reaction rate of high isotactic active centers reaches maximum at 85–90°C, and this effect contributes to both the highest isotacticity and the narrowest molecular weight distribution. For the MgCl2/TiCl4/phthalate ester‐AlEt3 catalyst system, the isotacticity of polypropylene remains approximately constant in the temperature range of experiments, which could be ascribed to elution of phthalate ester after the activation. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42487.

Construction of 3D micropatterned surfaces with wormlike and superhydrophilic PEG brushes to detect dysfunctional cells.

Detection of dysfunctional and apoptotic cells plays an important role in clinical diagnosis and therapy. To develop a portable and user-friendly platform for dysfunctional and aging cell detection, we present a facile method to construct 3D patterns on the surface of styrene-b-(ethylene-co-butylene)-b-styrene elastomer (SEBS) with poly(ethylene glycol) brushes. Normal red blood cells (RBCs) and lysed RBCs (dysfunctional cells) are used as model cells. The strategy is based on the fact that poly(ethylene glycol) brushes tend to interact with phosphatidylserine, which is in the inner leaflet of normal cell membranes but becomes exposed in abnormal or apoptotic cell membranes. We demonstrate that varied patterned surfaces can be obtained by selectively patterning atom transfer radical polymerization (ATRP) initiators on the SEBS surface via an aqueous-based method and growing PEG brushes through surface-initiated atom transfer radical polymerization. The relatively high initiator density and polymerization temperature facilitate formation of PEG brushes in high density, which gives brushes worm-like morphology and superhydrophilic property; the tendency of dysfunctional cells adhered on the patterned surfaces is completely different from well-defined arrays of normal cells on the patterned surfaces, providing a facile method to detect dysfunctional cells effectively. The PEG-patterned surfaces are also applicable to detect apoptotic HeLa cells. The simplicity and easy handling of the described technique shows the potential application in microdiagnostic devices.

Single ethylene molecular insertion as a probe into the nature of the active species in MgCl2-supported Ziegler–Natta catalysts

The propylene-ethylene copolymers with a very small amount of ethylene (from 0.01 to 1.8mol%) obtained with different catalyst systems at 100°C or 120°C were characterized by 13C NMR. The chain end group n-propyl formed through the chain transfer reaction of species to alkylaluminum following “one” ethylene molecule insertion was detected in these copolymers of low molecular weight. 13C NMR chain end group analysis of these copolymers implied that most of syndiotactic species in the MgCl2-supported Ziegler–Natta catalysts would be “dormant” for propylene insertion while highly isotactic species would remain highly active for propylene insertion when these two species were inserted by “one” ethylene molecule. For isotactoid species occasional “one” ethylene molecule insertions remarkably slowed down propagation of propylene. The active species could be divided into three classes according to their behavior following “one” ethylene molecule insertion, which fit Busico [1] three-state model of active species to a great degree. The chain end group ethyl (Et′) formed by chain transfer reactions by alkylaluminum at “one” ethylene molecule insertion followed by a 2-1-last-insertion was also detected by 13C NMR. Thus, the fraction of “dormant” polypropylene chains with a 2,1-last inserted unit was estimated to be in the 3–6mol% range for a TiCl4/MgCl2/diester-silane catalyst while for a TiCl4/MgCl2/diether catalyst the content of such the fraction was ca. 7–9mol%. 13C NMR analysis indicated that a large part of the “dormant” 2-1-inserted sites revived by “one” ethylene insertion were still “dormant” for propylene insertion at high polymerization temperature.

Ring-opening polymerization of ɛ-caprolactone with dilithium tetra-tert-butylzincate under mild conditions

We performed ring-opening polymerization (ROP) of ɛ-caprolactone with dilithium tetra-tert-butylzincate (TBZL) in toluene. TBZL is a bulky zincate complex with a range of unique reactivities such as unusually low basicity and high chemoselectivity; it is a metal catalyst of low toxicity. The initiating species for ROP of ɛ-caprolactone is, however, not the tert-butyl anion of TBZL but the hydroxyl anion derived from a trace amount of H2O in the system. Instead of a trace amount of H2O in the system, a known amount of benzyl alcohol (BnOH) was added as an ROP initiator. Poly(ɛ-caprolactone) with a BnO group at the initiating chain-end was obtained, as expected. 1H and 13C NMR spectra of a TBZL–BnOH mixture suggested the formation of a complex; the complex was the initiating species. The Mn increased linearly with increasing conversion. This means that the number of polymer chains is constant throughout the polymerization. The molecular weight distributions were relatively narrow, except with increased temperatures and/or prolonged polymerization times. This system does not need a high polymerization temperature or long polymerization time and uses a metal compound that has little effect on the environment. Poly(ɛ-caprolactone) with a narrow molecular weight distribution can therefore be obtained under mild conditions. Ring-opening polymerization (ROP) of ɛ-caprolactone with dilithium tetra-tert-butylzincate (TBZL) in toluene was performed. The initiating species for the ROP of ɛ-caprolactone is not the tert-butyl anion of TBZL but the hydroxyl anion derived from a trace amount of H2O or alcohol. Poly(ɛ-caprolactone) with a BnO group at the initiating chain-end was obtained by adding benzyl alcohol as an initiator, as expected. The molecular weight distributions were relatively narrow, except with increased temperatures and/or prolonged polymerization times. This system does not need a high polymerization temperature or long polymerization time.

Temperature effect on template polymerization of methacrylic acid using stereocomplex formation on quartz crystal microbalance substrates

ABSTRACTThe radical polymerization of methacrylic acid (MAA) at 0, 20, 40, and 70 °C was achieved in porous isotactic (it‐) poly(methyl methacrylate) (PMMA) films on quartz crystal microbalance (QCM) substrates, which were prepared by layer‐by‐layer assembled stereocomplex films of it‐PMMA and syndiotactic (st‐) poly(methacrylic acid) (PMAA), followed by the subsequent extraction of st‐PMAA. The MAA polymerization yields increased from 35 to 75%, as the polymerization temperature increased from 0 to 70 °C. Furthermore, infrared spectroscopy revealed that a higher polymerization temperature is necessary to form it‐PMMA/st‐PMAA stereocomplexes via stereoregular polymerization manner that resemble native it‐PMMA/st‐PMAA stereocomplexes. X‐ray diffraction pattern of porous it‐PMMA were also investigated for reaction fields. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 3032–3036

Dynamic mechanical analysis of high pressure polymerized urethane dimethacrylate

ObjectivesThe aim of this study was to compare the viscoelastic properties of high pressure (HP) polymerized urethane dimethacrylate (UDMA) with those of control, ambient pressure thermo-polymerized and photo-polymerized, UDMA and to assess the effect of varying polymerization parameters (protocol, temperature, and initiator) on the viscoelastic properties of HP polymerized UDMA. MethodsThe viscoelastic properties of the two control polymers, polymerized under atmospheric pressure, and four experimental polymers, polymerized under HP, were determined via dynamic mechanical analysis (DMA), in three point bending configuration. Atomic force microscopy (AFM) was used to characterize fractured polymer surface morphologies. ResultsThe results showed that: HP-polymerization lead to a polymer with significantly higher Tg and E′rub, indicative of a higher crosslink density; modifying the polymerization protocol resulted in a significant increase in tanδ; increasing the polymerization temperature lead to a significant decrease in E′rub and Tg; and that the polymer with no initiator had the lowest E′, E″, Tg, and E′rub and the highest tanδ, suggesting that under this conditions a polymer with significantly reduced crosslink density had been obtained. A characteristic nodular appearance was seen for the two control polymers under AFM, while a modified surface morphology was present in the case of HP polymerized materials. SignificanceThe DMA results suggest that polymerization under HP resulted in polymers with an increased crosslink density and that the higher polymerization temperature or the lack of initiator was detrimental to the viscoelastic properties determined. Changes in polymer network morphology were identified by AFM characterization.

Ring-opening copolymerization of CHO and MA catalyzed by mononuclear [Zn(L2)(H2O)] or trinuclear [Zn3(L2)2(OAc)2] complex based on the asymmetrical bis-Schiff-base ligand precursor

Based on the half-unit Schiff-base ligand precursor HL1 and the asymmetrical bis-Schiff-base ligand precursor H2L2 synthesized from the reaction of 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (PMBP), o-phenylenediamine and/or o-vanillin, three complexes containing low toxicity Zn2+ ions, mononuclear [Zn(L1)2] (1), [Zn(L2)(H2O)] (2) and trinuclear [Zn3(L2)2(OAc)2] (3), are obtained, respectively. Complex 1 proves to be inactive, resulting from its saturated octahedral coordination environment around the central Zn2+ ion, while in complex 2 or 3, the unsaturated five and/or four-coordinate coordination environment for the catalytic active centers (Zn2+ ions) permits the monomer insertion for the effective bulk or solution copolymerization of CHO (cyclohexene oxide) and MA (maleic anhydride). All the bulk copolymerizations afford poly(ester-co-ether)s, while some of the solution copolymerizations produce perfectly alternating polyester copolymers. Moreover, higher polymerization temperature, lower catalyst and co-catalyst concentration and shorter reaction time are helpful for the formation of alternating copolymers in bulk or solution copolymerization. Of the three co-catalysts, DMAP (4-(dimethylamino)pyridine) is found to be the most efficient, while an excess thereof is detrimental for chain growth of the copolymers.

Synthesis of highly reactive polyisobutylenes with exo-olefin terminals via controlled cationic polymerization with H2O/FeCl3/iPrOH initiating system in nonpolar hydrocarbon media

Cationic polymerizations of isobutylene (IB) with H2O/FeCl3/isopropanol (iPrOH) initiating system were conducted in nonpolar hydrocarbon media, such as n-hexane or mixed C4 fractions at −40 to 20 °C. This cationic polymerization is a chain-transfer dominated process via highly selective β-proton elimination from CH3 in the growing chain ends, leading to formation of highly reactive polyisobutylenes (HRPIBs) with large contents (> 90 mol %) of exo-olefin end groups (structure A). The content of structure A remained nearly constant at about 97 mol % during polymerization and isomerization via carbenium ion rearrangement could be suppressed in nonpolar media. First-order kinetics with respect to monomer concentration was measured for selective cationic polymerization of IB in the mixed C4 fraction feed at −30 °C and the apparent rate constant for propagation was 0.028 min−1. High polymerization temperature (Tp) or [FeCl3] accelerate β-proton elimination or isomerizations and simultaneously decrease selectivity of β-proton abstraction from CH3. Molecular weight decreased and molecular weight distribution (MWD) became narrow with increasing Tp or [FeCl3]. To the best of our knowledge, this is the first example to achieve high quality HRPIBs with near 100% of exo-olefin terminals and relatively narrow MWD (Mw/Mn = 1.8) by a single-step process in nonpolar hydrocarbon media. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4200–4212

Influence of Synthesis Processes on the Properties of PVAc-MMT-STAB Exfoliated Nanocomposites

Five different processes were designed based on the polymerization time and water amount to investigate their influence on the properties of exfoliated nanocomposites synthesized by vinyl acetate (VAc) and montmorillonite-octadecyl trimethyl ammonium bromide (MMT-STAB). The violent stirring, low MMT-STAB content, high polymerization temperature, favorable polymerization time and suitable water amount were very important. PVAc-MMT-STAB had high static tensile and good dispersion. PVAc's linear macromolecular chains were formed in MMT-STAB layers that was exfoliated into layers or sheets of nanoparticles and dispersed randomly. They dispersed together to form the structures of “Strawberry,” “Swallow,” “Tactoids,” “Half Core-Shell” and “Similar Core-Shell”.

Synthesis and characterization of novel adamantane‐based copoly(aryl ether ketone)s with low dielectric constants

AbstractA series of novel adamantane‐based copoly(aryl ether ketone)s (PAEK‐CF3‐Ad) with low dielectric constants were prepared by post‐amidation of copoly(aryl ether ketone)s containing (3‐trifluoromethyl)phenyl and carboxyl groups with 4‐adamantylaniline. Compared with the preparation of adamantane‐containing poly(aryl ether ketone)s by direct polymerization of adamantyl‐substituted monomers, this side‐chain grafting method avoids various problems, such as high polymerization temperature and the difficult polymerization of adamantyl‐substituted monomers. The dielectric, thermal and mechanical properties of the synthesized PAEK‐CF3‐Ad were characterized using a precision impedance analyzer, differential scanning calorimetry and thermogravimetric analysis, and a universal tester, respectively. The results indicate that PAEK‐CF3‐Ad films exhibited low dielectric constants ranging from 2.33 to 2.65 at 1 MHz due to the introduction of the adamantyl groups. The synthesized PAEK‐CF3‐Ad copolymers exhibited good thermal and mechanical properties. © 2013 Society of Chemical Industry

High-conversion synthesis of poly(3,4-ethylenedioxythiophene) by chemical oxidative polymerization

High-conversion synthesis of poly(3,4-ethylenedioxythiophene) (PEDOT) by chemical oxidative polymerization was studied. Hydrolysis of oxidative agent, and effects of polymerization temperature and time were taken into account. Unlike iron chloride, the oxidative agent of iron sulfate can be effectively used at high temperature, due to the absence of obvious hydrolysis. In addition, high polymerization temperature and long reaction time led to dramatically increase of conversion. Moreover, the structure, morphology and electrical conductivity of the prepared PEDOT with high-conversion had not been changed obviously, when compared with the common low-conversed product obtained at low temperature with short reaction time.

Titanium complex bearing 8‐anilino‐1‐naphthalenesulfonate ligand: Synthesis and catalytic behavior toward ethylene (co‐)polymerization

AbstractA novel titanium complex bearing 8‐anilino‐1‐naphthalenesulfonic acid was synthesized. The effects of cocatalyst and reaction conditions on ethylene polymerization were studied. The synthesized titanium complex exhibited high polymerization activity in the presence of MAO cocatalyst. The synthesized titanium complex/MAO catalyst system showed a uniform active site and was very stable at high polymerization temperature. In addition, the copolymerization of ethylene and norbornene was investigated. With the introduction of norbornene, the catalyst activity slightly decreased with MAO as cocatalyst but increased with TEA as cocatalyst. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Effects of Polymerization and Crosslinking Technologies on the Crystallization Behaviors and Gel Network of Crosslinked Polyethylene

In the present study, we investigated the influences of polymerization and crosslinking technologies on the branched-chain structures, crystallization behaviors, and gel networks of two types of low-density polyethylenes, LDPE1 and LDPE2, polymerized under different polymerization conditions in commercial large-capacity production lines. High temperature 13C NMR analysis suggests that the molar contents of both long-chain branches and short-chain branches of LDPE2 were markedly higher than those of LDPE1 due to a higher polymerization temperature for LDPE2. The high content of chain branches of LDPE2 leads to its relatively higher storage modulus, entanglement density, and gel content, as indicated by dynamic mechanical analysis. In addition, when the crosslinking temperature reached 180°C, the LDPE2 crosslinked with 2 wt% dicumylperoxide (XLPE2-D2) displayed a relatively wider processing time window and a faster crosslinking rate than XLPE1-D2. Successive self-nucleation and annealing fractionation indicated that increasing the concentration of dicumylperoxide can improve the crosslinking degree, but resulted in lower crystallinity and thinner lamellar crystals.