m-PEG8-t-butyl ester - ≥98%

Cat. No.: M596808

GRADE & PURITY ≥98%

Storage

Store at -20°C

Shipped In

Ice chest + Ice pads

Overview

m-PEG8-t-butyl ester is a PEG derivative containing a t-butyl ester. The t-butyl protected carboxyl group can be deprotected under acidic conditions. The hydrophilic PEG spacer increases solubility in aqueous media.

Specifications

Specifications & Purity

≥98%

Storage

Store at -20°C

Shipped In

Ice chest + Ice pads

This product requires cold chain shipping. Ground and other economy services are not available.

Purity

≥98%

Application Protocols

No manufacturer‑validated biological assay protocols (e.g., WB, IHC, IF, FC) are associated with this materials‑science reagent.

General workflow outlines (informational; adapt to your system):

• Deprotection to m‑PEG‑COOH:
  1. Dissolve m‑PEG8‑tBu ester in dry DCM (5–20 mg/mL).
  2. Add TFA to 50–95% v/v at 0–25°C; stir 1–2 h.
  3. Monitor by 1H NMR; remove volatiles; co‑evaporate with toluene; dry under high vacuum.
• NHS‑ester formation and coupling to amines:
  1. Dissolve m‑PEG‑COOH in dry DMF (or DCM).
  2. Add EDC (1.2 eq) and NHS (1.2 eq); stir 0.5–1 h at 0–25°C.
  3. Add amine‑containing target in buffered medium (pH 7.4–8.0); react 1–4 h; quench with ethanolamine.
• Surface grafting (amine‑functional substrates): Prepare NHS‑PEG solution freshly; immerse substrate or mix with particles under controlled pH and ionic strength; rinse thoroughly to remove unbound polymer.

Note: The above are general literature practices and not product‑specific, validated protocols. Optimize concentrations, times, and solvent systems for your application. Always perform small‑scale pilots before scale‑up.

Biological Roles

No biological identity (enzyme, metabolite, ligand) is assigned to this synthetic PEG derivative.

General PEG‑related context (informational, non‑clinical):

• PEG chains are hydrophilic, nonionic polymers known for reducing protein adsorption and minimizing nonspecific interactions at interfaces. This “stealth” behavior derives from high chain mobility, water structuring, and entropic repulsion (literature/general).
• In materials and biochemical assay design, PEGylated surfaces can limit fouling, modulate hydrodynamic radius, and increase apparent solubility of conjugated cargos.
• The tert‑butyl ester masking group serves no biological function; it is a protecting group intended for chemical processing. Post‑deprotection, the carboxylate can be used to attach biomolecules (via amide or other linkages) to create PEGylated constructs for in vitro research.
• PEGs are generally considered biologically inert in lab contexts; however, at sufficient concentrations they can influence osmotic pressure and viscosity in solutions and hydrogels.

Caution: This product is for research use only. It is not intended for diagnostic, therapeutic, or clinical use. Any biological testing should be confined to in vitro or materials‑focused research workflows following institutional safety approvals.

Buffer Applications

This reagent is not a buffer component and does not form defined acid–base buffer systems in its protected (tert‑butyl ester) form.

Practical notes (general):

• After deprotection to the free acid, the terminal –COOH can contribute to solution pH but is not used as a dedicated buffering species. Carboxylic acids have limited buffering capacity near pH ~4–5 (literature/general) and are typically not chosen when precise buffering is required.
• For conjugation workflows in aqueous media post‑deprotection, select established buffers appropriate to your coupling chemistry (e.g., MES pH 5.5–6.5 for EDC/NHS activation; phosphate or HEPES pH 7.2–7.8 for amide formation). Avoid primary amine‑containing buffers (e.g., Tris) during NHS‑ester coupling to prevent side reactions.

If your application requires a particular buffer system for coupling or processing, follow validated protocols for that buffer and verify compatibility with PEGylated substrates.

Green Alternatives

Green chemistry considerations for PEG‑based ester handling focus on solvent choice, reagent hazards for deprotection, and waste minimization. While the PEG scaffold itself is often viewed favorably due to low volatility and aqueous compatibility, process chemicals can dominate the environmental footprint.

Comparison of common choices (literature/general; not item‑specific):

• Deprotection acid: TFA (highly effective, volatile, corrosive) vs. greener acids (e.g., aqueous HCl, methane sulfonic acid). TFA offers rapid, clean tert‑butyl cleavage at ambient temperature but carries persistence concerns; methanesulfonic acid or HCl in less hazardous solvents can be alternatives, albeit with slower rates or higher temperatures.
• Solvents:
  • Prefer ethyl acetate, MeOH/EtOH, 2‑MeTHF, CPME, or propylene carbonate where compatible.
  • Avoid chlorinated solvents when possible; if DCM is needed for tBu cleavage, minimize volume and use efficient recovery.
• Coupling chemistry: Shift from carbodiimide with stoichiometric additives to catalytic or enzyme‑mediated couplings when feasible (e.g., DMTMM in water can reduce urea waste relative to EDC/HOBt). Evaluate safety of additives; avoid HOBt due to explosivity risk.
• Workup/waste: Design aqueous workups to enable phase separation and solvent recycling; use solid‑supported scavengers to minimize solvent usage.

Trade‑offs:

• Greener acids/solvents may lengthen reaction times or lower selectivity for sensitive substrates. Pilot small‑scale trials are recommended to balance EHS benefits against performance.

Pharmaceutical Uses

No pharmacopeial grade or excipient designation is provided for this item; it is supplied for research use only.

General information on PEG derivatives in formulation science (informational, non‑clinical):

• PEGs are widely used as processing aids and excipients (solubilizers, plasticizers, viscosity modifiers) due to their water miscibility and low volatility. However, end‑functional PEG esters like m‑PEG‑tBu are synthetic intermediates, not typical excipients.
• The tert‑butyl ester serves as a protecting group during synthesis of PEGylated actives or materials; it is generally removed before any formulation use to expose the functional –COOH for further derivatization (e.g., conversion to NHS esters, amide formation).
• For in vitro prototype formulations (e.g., nanoparticle coatings, assay reagents), the monomethoxy PEG architecture offers antifouling character and can tune colloidal stability after covalent attachment to surfaces or ligands.

Compliance note:

• This catalog item is not intended for human or veterinary applications, diagnostic procedures, or for use as a GMP excipient. If excipient‑grade PEGs are required, source materials that explicitly state pharmacopeial compliance (e.g., USP/NF, Ph. Eur.) and include full regulatory documentation.

Physical Properties

Item-specific numeric specifications are not provided for this SKU; consult the CoA/Spec Sheet for definitive values.

General/literature characteristics for m‑PEG8‑tert‑butyl esters (informational only; not item specifications):

• Physical state: Typically a white to off‑white waxy solid or viscous syrup at room temperature (varies with n and dispersity).
• Solubility (typical):
  • Miscible with many organic solvents (DCM, chloroform, THF, acetone, MeOH, EtOH, acetonitrile, DMF, DMSO).
  • Highly soluble in water for low oligomers; water solubility remains good for PEG8 though hydrophobic end groups can slightly reduce it versus m‑PEG‑OH (literature/general behavior).
• Density, refractive index: Not specified for this item; refer to CoA/Spec Sheet.
• pKa: Not applicable to the protected ester; after deprotection the terminal acid exhibits typical carboxyl pKa (~4–5; literature/general).
• Boiling/Melting points: PEG oligomers show broad, concentration‑ and n‑dependent transitions; discrete BP/MP are not meaningful for polydisperse PEGs. Not specified for this item.
• Hygroscopicity: PEGs are mildly hygroscopic; they can absorb moisture which may affect weighing and coupling reactions (general behavior).
• Viscosity: Increases with molecular weight and concentration; PEG8 solutions are generally low to moderate viscosity.

Important: Treat any numeric property needs as method‑ and batch‑dependent for PEGs; obtain or measure values under your exact conditions when critical.

Quality & Grades

• Grade/Purity: Not specified for this item; refer to CoA/Spec Sheet.

Guidance on interpreting PEG reagent quality (general):

• Purity reporting: PEGs are often characterized by NMR (1H/13C), FT‑IR, and MALDI‑TOF/ESI MS for average molecular weight. Residual solvents, monomer content, and low‑MW species may be reported. For coupling applications, low residual acidic/alkaline impurities and minimal peroxide/oxidation byproducts are preferred.
• Polydispersity: Because PEGs are distributions, the Polydispersity Index (PDI, Mw/Mn) influences performance in surface modification and conjugation. Narrower PDI supports better batch‑to‑batch reproducibility. The PDI for this item is not specified; consult the CoA.
• Functional titration: For end‑functional PEGs, effective functionality (meq/g) or substitution level may be provided. This is critical for stoichiometric conjugations; check the CoA.
• Stabilizers: None specified for this item. If stabilizers are used in PEG reagents, they should be disclosed on the CoA; stabilizers can interfere with some coupling chemistries.
• UV/Chromatography: In HPLC contexts, PEGs can show strong baseline effects; HPLC grade solvents and clean reagents reduce background. No UV cutoff/absorbance spec is provided for this item.

Recommendation: For sensitive materials or bioconjugation workflows, verify lot data (Mn/Mw, PDI, residuals) and perform a small‑scale test coupling to validate performance before committing to production scale.

Reaction & Applications

m‑PEG8‑tert‑butyl ester is a protected, monofunctional PEG platform enabling controlled introduction of a terminal carboxyl group upon demand. It is suited for materials science and bioconjugation workflows where temporary masking of acidity is advantageous.

Representative applications (general/literature):

• Protecting‑group strategy: The tert‑butyl ester masks the carboxylate to improve solubility in nonpolar media and to avoid premature salt formation during synthesis or processing. Rapid, acid‑triggered deprotection restores the –COOH without hydrogenolysis.
• Surface/particle modification: After deprotection, the carboxyl terminus can be activated (EDC/NHS) to graft PEG onto amine‑bearing substrates (polymers, silica, magnetic nanoparticles), imparting protein‑resistant, hydrophilic surfaces.
• Polymer conjugation: End‑functional PEG provides spacing/linker effects in polymer brushes, hydrogels, and block copolymers. The m‑PEG architecture prevents crosslinking by ensuring monofunctionality.
• Probe/ligand spacing: Following conversion to PEG‑acid (then to NHS‑ester), enables attachment to amines on small molecules, peptides, or dyes to modulate solubility and reduce nonspecific binding.
• Microfabrication/coatings: Temporary hydrophobicity from the protected end can aid film formation from organic media; post‑deprotection restores hydrophilicity for aqueous compatibility.

Practical notes:

• Keep moisture low during acidolysis to control rates and minimize hydrolysis of other acid‑sensitive groups.
• After deprotection, neutralize and rapidly remove volatile acid under reduced pressure; azeotrope with toluene or add co‑solvent (MeOH) for efficient TFA removal.
• Confirm deprotection by 1H NMR (disappearance of tert‑butyl singlet near ~1.4 ppm; literature/general) and by titration of acid equivalents.

Reaction Conditions

The following are general literature guidelines for handling tert‑butyl ester deprotection and subsequent coupling steps with m‑PEG derivatives. They are not specifications for this item.

Deprotection (tBu → COOH; acidolysis):

• Reagents: TFA (50–95% v/v) in DCM or neat; alternatives include HCl (anhydrous) in dioxane or methanesulfonic acid in an appropriate solvent.
• Solvent: Anhydrous DCM, DCE, or TFE. Avoid water to maintain rate and prevent side hydrolysis.
• Temperature/time: 0–25°C, 0.5–4 h, depending on acid strength and concentration. Monitor by 1H NMR (loss of tert‑butyl singlet at ~1.4 ppm; literature/general) or by IR (loss of tBu C–O stretch) and by titration of acid.
• Workup: Co‑evaporate with toluene or MeOH to remove TFA; neutralize residual acid with aqueous bicarbonate if compatible; dry thoroughly (vacuum, mild heat) to remove volatiles.

Activation and coupling (post‑deprotection):

• NHS‑ester formation: EDC (1.1–1.5 eq) + NHS (1.1–1.5 eq) in dry DMF or DCM at 0–25°C for 0.5–2 h; then couple to amines in buffered aqueous or mixed solvent at pH 7.2–8.3. Alternative: DIC/DMAP or DMTMM in aqueous media.
• Acid chloride route: SOCl2 or oxalyl chloride (2–5 eq) with catalytic DMF in DCM or toluene, 0–25°C, 0.5–2 h; promptly quench into amine nucleophile. Use caution—polyether backbones can degrade under harsh conditions.

General tips:

• Dry reagents and solvents limit side reactions (e.g., hydrolysis during activation).
• Adjust stoichiometry based on effective functionality (meq/g) specific to your lot.
• For surface grafting, pre‑activate immediately before contacting the substrate to minimize hydrolysis of active esters.

Safety & Handling

Hazard classification for this specific item is not provided here. Always review the SDS supplied with your lot for authoritative safety information.

Item-specific hazard data:

• Signal word: Not specified for this item; refer to SDS.
• H‑statements: Not specified for this item; refer to SDS.
• GHS classification and pictograms: Not specified for this item; refer to SDS.

General handling guidance for PEG tert‑butyl esters (informational):

• PPE: Wear lab coat, safety glasses, and appropriate chemical‑resistant gloves. Use in a well‑ventilated area or fume hood when weighing or dissolving.
• Incompatibilities: Avoid strong oxidizers and strong acids/bases. Note that tert‑butyl esters are acid‑labile; exposure to strong acids (e.g., TFA, HCl) can deprotect to the free acid.
• Thermal/chemical stability: Typically stable at ambient conditions under dry, neutral pH. Prolonged heating in acidic media promotes deprotection.
• First aid (overview; defer to SDS):
  • Skin/eye contact: Rinse with water for several minutes; remove contaminated clothing; seek medical advice if irritation persists.
  • Inhalation: Move to fresh air; seek medical attention if symptoms occur.
  • Ingestion: Rinse mouth; do not induce vomiting; seek medical attention.
• Spill response: Absorb viscous material with inert absorbent; collect for disposal. Wash area with soap and water.
• Waste: Dispose in accordance with institutional and local regulations; avoid drain release.

Note: PEGs have low volatility; inhalation risk is generally minimal compared to volatile solvents, but powdered forms can create nuisance dust.

Solvent Selection

This PEG‑based ester is amphiphilic: the polyether chain imparts hydrophilicity, while the tert‑butyl ester is nonionic and relatively hydrophobic. Solvent choice should reflect the intended operation (dissolution, deprotection, coupling, coating).

General miscibility/selection guidance (literature/general):

• Highly compatible: DCM, chloroform, THF, acetone, MeOH, EtOH, isopropanol, acetonitrile, DMF, DMSO, dioxane. These typically give rapid dissolution at room temperature.
• Aqueous media: m‑PEG8 derivatives remain water‑soluble to moderately water‑soluble; gentle warming (30–40°C) and pre‑wetting with alcohol can aid dissolution.
• For acidolysis (tBu deprotection): Use anhydrous DCM, DCE, or TFE in combination with TFA (see Reaction Conditions). Avoid water during protection/deprotection steps to control rates.
• For amide coupling post‑deprotection: DMF, DMSO, NMP, or aqueous buffered systems (pH 6–8) are typical, selected based on partner solubility and chosen coupling chemistry (e.g., EDC/NHS).

Small comparison (general):

• DCM: Fast dissolution; ideal for TFA deprotection; low boiling for easy removal; halogenated waste burden.
• DMF/DMSO: Excellent solvent for coupling; high boiling; thorough drying recommended to avoid hydrolysis during activation.
• Alcohols (MeOH/EtOH): Green(er) options for dissolution and washing; may participate in transesterification under strong acid/base—avoid in such conditions.

Tip: Filter warm solutions (0.2–0.45 µm) to remove particulates prior to thin‑film coatings or lithography workflows.

Storage & Reconstitution

• Storage conditions (from Product Data): Store at −20°C.
• Shipping (from Product Data): Shipped in ice chest with ice pads.

Handling and reconstitution (general guidance for PEG esters):

• Upon receipt: Allow the sealed container to equilibrate to room temperature before opening to prevent moisture condensation.
• Containers: Keep tightly closed under dry, inert atmosphere if possible. Consider aliquoting into moisture‑free vials to minimize repeated freeze‑thaw and headspace humidity.
• Solid/waxy materials: If semi‑solid at room temperature, gently warm (30–40°C) to facilitate transfer; avoid prolonged heating.
• Reconstitution solvents: Anhydrous DCM, THF, acetone, MeOH/EtOH, acetonitrile, DMF, or DMSO. Select based on downstream use (e.g., DCM for acidolysis; DMF/DMSO for coupling). Filter solutions (0.2–0.45 µm) when clarity is essential.
• Stability: tert‑Butyl esters are stable under neutral, dry storage; avoid exposure to strong acids which will deprotect to the free acid. Minimize light and air exposure to limit oxidative degradation of the polyether over long storage.
• Shelf life: Not specified for this item; refer to CoA/Spec Sheet. For best results, prepare fresh solutions and avoid prolonged storage in reactive solvents (especially in the presence of acids or bases).

Research Use: For research use only (from Product Data).

Structure & Identity

A monofunctional, end-protected polyethylene glycol derivative designed for materials and conjugation workflows. The name indicates a monomethoxy PEG with approximately eight ethylene oxide repeat units and a terminal carboxyl masked as a tert‑butyl ester.

• Item-specific identifiers (CAS, InChIKey, SMILES, Molecular Formula, Molecular Weight): Not specified for this item; refer to CoA/Spec Sheet.
• Structural features (general/literature description):
  • Linear polyether backbone consisting of ~8 –CH2CH2O– repeat units (PEG8).
  • One terminus capped with a methoxy group (m‑PEG, i.e., –OCH3), rendering the chain monofunctional.
  • Opposite terminus bears a carboxylic acid protected as a tert‑butyl ester (–COOtBu), providing acid‑labile protection.
  • Overall architecture: CH3O–(CH2CH2O)n–(linker)–C(=O)OtBu, where n≈8 (distribution typical for PEGs).
  • No stereocenters; flexible, nonionic, hydrophilic polyether chain.
• 2D structure in words: a linear, repeating –CH2–CH2–O– chain (eight units on average), with a methoxy cap at one end and a carbonyl linked to a tert‑butyl ester at the other end.
• Polydispersity (general): Commercial PEGs are commonly supplied as narrow distributions around the target n; exact PDI for this item is not specified; refer to CoA/Spec Sheet.

Notes: Because PEGs are typically distributed oligomers, exact molecular weight and formula for this catalog item are batch‑specific. Always consult the CoA for lot‑specific identity parameters.

Synthetic Utility

m‑PEG8‑t‑butyl ester serves as a versatile, monofunctional PEG building block in protection–deprotection and end‑group transformation sequences.

Key functional elements and reactivity (general/literature):

• tert‑Butyl ester (–COOtBu): Acid‑labile protecting group for carboxylic acids. Rapidly cleaved by strong acids (TFA, HCl, BF3·OEt2) to yield the corresponding m‑PEG‑acid. Resistant to most neutral and basic conditions, enabling orthogonal strategies alongside base‑sensitive motifs.
• Polyether chain: Chemically robust under many conditions; avoid strong oxidants and electrophiles that can cause macromolecular degradation.
• Monomethoxy cap: Ensures monofunctional behavior, preventing undesired crosslinking during coupling.

Typical transformations enabled:

• Deprotection: tBu ester → acid (m‑PEG‑COOH).
• Activation: Acid → active ester (NHS, PFP), acid chloride (with oxalyl chloride or SOCl2; take care to control conditions with PEGs), or mixed anhydrides.
• Coupling: Formation of amides with amines (EDC/NHS, DMTMM), esters with alcohols (DCC/DMAP), or thiol‑reactive handles after downstream conversion (e.g., maleimide introduction via amide linkage).
• Surface attachment: Carboxyl activation enables grafting to amine‑functional substrates (polymers, particles, inorganic surfaces), creating antifouling layers and spacers.

Advantages:

• Controlled introduction of acid functionality on demand, improved processability in organic media during protected stages, and reduced side reactions from premature ionization.

Verify lot‑specific functionality (meq/g) and Mn before stoichiometric planning.

Target Specificity

Not applicable. This product is a synthetic polymer reagent, not an antibody, probe, or biological targeting molecule. No antigen, epitope, clone, isotype, or species reactivity is associated with this SKU.

Frequently Asked Questions

What is the purity of this product?

This product is supplied at ≥98% purity (chemical assay). Lot-specific values are stated on the Certificate of Analysis.

How should this product be stored?

Store at ?20 °C. Freezer storage is required to maintain the specified shelf life.

How is this product shipped?

This product ships in an insulated container with ice pads. Unpack on arrival and transfer it to the storage condition stated above.

What documentation is provided?

Available product documentation, including Certificates of Analysis (COA), Safety Data Sheets (SDS), and specification sheets, is shown in the product document area. Document availability and access follow the current site policy.