Pilot Plant Preparation of Polystyrene of Very Narrow Molecular Weight Distribution

Altares, Timothy; Clark, Edward L.

doi:10.1021/i360034a009

Cited by 12 publications

(3 citation statements)

References 4 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Because of the flexible S−C linkage attached to 11 C−C bonds located at one chain end, PS/RSH/3.7k exhibits more than a 10 K reduction in T g (334.1 K) compared to the PS standard (345.6 K) which has much shorter sec-butyl/ H chain ends. 70 The PS/EtBriB/3.6k sample has a T g that is 2.5 K higher than that of PS/Anionic/3.6k. Overall, initiator fragments derived from polymerization initiators at chain ends of ∼4 kg/mol PS can dramatically tune T g by as much as ∼33 K.…”

Section: Resultsmentioning

confidence: 92%

“…Figure b shows similar heat capacity curves for M n = ∼4 kg/mol PS synthesized by pseudoliving polymerization as well as PS/Anionic/3.6k. Because of the flexible S–C linkage attached to 11 C–C bonds located at one chain end, PS/RSH/3.7k exhibits more than a 10 K reduction in T g (334.1 K) compared to the PS standard (345.6 K) which has much shorter sec -butyl/H chain ends . The PS/EtBriB/3.6k sample has a T g that is 2.5 K higher than that of PS/Anionic/3.6k.…”

Section: Resultsmentioning

confidence: 96%

“…Because of the high chain-end concentration, PS/Anionic/3.6k exhibits T g,onset = 345.6 K, much lower than the T g,onset of ∼374 K for high MW PS. By simply changing the chain-end structures from sec -butyl and H atoms in PS/Anionic/3.6k to cyanopentanoic acid groups in PS/ACVA/4.1k, the T g increases by more than 20 K to 367.0 K. ( T g,onset and T g,(1/2)Δ Cp values differ by 2–3 K; we use T g = T g,onset in the following text.) The unusually high T g for PS/ACVA/4.1k may be understood to arise from the bulky ACVA initiator fragments (rather than small sec -butyl groups and hydrogen atoms) being at PS chain ends.…”

Section: Resultsmentioning

confidence: 99%

See 2 more Smart Citations

Dramatic Tunability of the Glass Transition Temperature and Fragility of Low Molecular Weight Polystyrene by Initiator Fragments Located at Chain Ends

et al. 2016

View full text Add to dashboard Cite

Important, yet unexplored effects of chemically distinct initiator fragments incorporated at chain ends in linear polymer are investigated in depth. Polystyrene (PS) samples of a wide range of molecular weight (MW) were synthesized by conventional free radical polymerization and controlled radical polymerization using seven different initiators and compared with anionically polymerized PS. The initiator fragments incorporated during polymerization have major consequences on the glass transition temperature (T g) and dynamic fragility of low MW PS. For example, with ∼4 kg/mol PS, the T g onset value and fragility can be tuned from ∼334 K and ∼65, respectively, with dodecanethiol and hydrogen atom chain ends to ∼367 K and ∼130, respectively, with cyanopentanoic acid chain ends. A similar high T g and high fragility were measured with isobutyric acid/SG1 nitroxide chain ends. These remarkable effects, with a greater than 30 K difference in T g and a factor of 2 difference in fragility, indicate that chain ends in low MW PS homopolymer play an “outsize” role in comparison to comonomer units in perturbing properties that are sensitive to the density of chain ends. The T g results also provide further direct evidence against any correlation between the MW at which the T g–MW dependence saturates and entanglement MW. Instead, the perturbation of T g by the combined effects of a reduction in MW (increase in chain-end density) and chain-end structure correlates one-to-one within error with the perturbation of fragility. These results suggest that the susceptibility of fragility to be perturbed is key to the susceptibility of T g to be perturbed.

show abstract

Section: Resultsmentioning

confidence: 92%

Section: Resultsmentioning

confidence: 96%

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Dramatic Tunability of the Glass Transition Temperature and Fragility of Low Molecular Weight Polystyrene by Initiator Fragments Located at Chain Ends

et al. 2016

View full text Add to dashboard Cite

show abstract

The T_ll (>T_g) transition of atactic polystyrene

Stadnicki

Gillham

Boyer

1976

J of Applied Polymer Sci

105

View full text Add to dashboard Cite

SynopsisTorsional braid analysis (TBA) ( 4 . 3 Hz) and differential thermal analysis (DTA) data are presented for the temperature region 0-200°C for two series of atactic polystyrenes with narrow molecular weight distributions: (a) anionic series, M n = 6O0-2X1O6, MW/Mn N 1.1; (b) fractionated thermal series, @, , = 2,000-l.lX105, Mw/M ,, (1.25. Preliminary results on bimodal blends are also reported. Heating and cooling cycles were employed with TBA; only the heating mode was used with DTA. In addition to a dynamic mechanical loss peak a t T,, a higher temperature loss peak was also found. Designated the Tu or liquid-liquid transition (relaxation), its temperature is 1.1 to 1.2 T, ( O K ) for polymers with molecular weight below the critical molecular weight (M,) for chain entanglements. Above M, a? 35,000, it rises steeply, being c=2OO0C for @, , = 110,000. The common dependence of T, and Tii on &f,,-l below M, suggests a common molecular origin. The two facts, (a) that Ti1 > Tg and (b) that Ti1 reflects chain entanglements, further suggest that Ti1 involves a longer chain segment length and possibly the entire molecule. Comparison of 7 ' " versus log M plots with T versus log M isoviscous state plots based on zero-shear melt viscosity data from the literature implies that Tii-as measured by the TBA technique corresponds to an isoviscous state of 104-105 poises. The employment of narrow molecular weight polymers is presumably responsible for both the linear variation of the Ti1 transition with & f n -l (which suggests a free volume basis for the relaxation) and the form of the variation of the Ti1 transition with log M (which suggests an isoviscous basis for the relaxation). The sharpness of the Ti1 loss peak by TBA decreases with increasing molecular weight and dispersity. The DTA endothermic event corresponding to Ti! is clearly related to the occurrence of flow since the fused films which result from heating granules to 200'C and cooling to R.T. do not reveal a Tli on reheating. If a fused film is crushed, a Ti1 event is observed on heating. For bimodal blends with M,, < M, for both components, the Ti1 transition was averaged; with one component less than and one greater than M,, the Ti1 transitions of the components appeared to occur independently at temperatures corresponding to those of the isolated components. In accordance with Ueberreiter and Orthmann, T, appears to separate a glassy state from a fixed liquid state, whereas T11separates the fixed liquid from a true liquid state. Possible molecular interpretations for the Ti1 process are discussed. Systematic bodies of data from the literature which indicate the presence of the Ti1 process in other polymers are summarized.

show abstract

Electron‐beam lithography of chlorinated polystyrenes with narrow molecular weight distributions

Feit¹,

Stillwagon²

1980

Polymer Engineering & Sci

View full text Add to dashboard Cite

Polystyrenes with narrow molecular weight distributions have been chlorinated with only slight broadening of molecular weight distributions to yield materials that are five to six times more sensitive to electron‐beam irradiation. The chlorinated polystyrenes are useful negative resists for electron‐beam lithography. At molecular weights of 3‐4 × 105g/mole, their threshold sensitivities to 20 keV electrons are 1‐2μC/cm2. Their lithographic contrasts are ≥ 1.5; in fact, > 2.0 for the narrowest molecular weight distributions. They compare favorably in these regards to polystyrenes of similar molecular weight characteristics. Lithographic relief images that are 80% of the original thickness of the polymer film can be formed at three to four times the threshold dose. The degree of chlorination ranged from 0.65‐0.76 Cl/monomer unit. The infrared spectra of the chlorinated materials resemble the spectrum for poly(4‐chlorostyrene). Elemental analysis indicated, however that some addition of chlorine had occurred. More extensive chlorination or chlorination of the higher molecular weight starting materials broadened the molecular weight distributions. The chlorinated material, a kind of poly(4‐chlorostyrene‐costyrene), is less sensitive than poly(4‐chlorostyrenc) prepared by addition polymerization by almost a factor of four.

show abstract

Pilot Plant Preparation of Polystyrene of Very Narrow Molecular Weight Distribution

Cited by 12 publications

References 4 publications

Dramatic Tunability of the Glass Transition Temperature and Fragility of Low Molecular Weight Polystyrene by Initiator Fragments Located at Chain Ends

Dramatic Tunability of the Glass Transition Temperature and Fragility of Low Molecular Weight Polystyrene by Initiator Fragments Located at Chain Ends

The T_ll (>T_g) transition of atactic polystyrene

Electron‐beam lithography of chlorinated polystyrenes with narrow molecular weight distributions

Contact Info

Product

Resources

About

Pilot Plant Preparation of Polystyrene of Very Narrow Molecular Weight Distribution

Cited by 12 publications

References 4 publications

Dramatic Tunability of the Glass Transition Temperature and Fragility of Low Molecular Weight Polystyrene by Initiator Fragments Located at Chain Ends

Dramatic Tunability of the Glass Transition Temperature and Fragility of Low Molecular Weight Polystyrene by Initiator Fragments Located at Chain Ends

The Tll (>Tg) transition of atactic polystyrene

Electron‐beam lithography of chlorinated polystyrenes with narrow molecular weight distributions

Contact Info

Product

Resources

About

The T_ll (>T_g) transition of atactic polystyrene