Table 3.

Conditions of preparation of polymorphs by mechanical activation.

#	Sample	Obtained Polymorph	Mill Type	Milling Cell	Ball (#, Material) Sample Weight	Milling Frequency	Milling Temperature	Milling Time and Solvent	Ref.
1P	Ranitidine hydrochloride	Ranitidine hydrochloride, form 2	Oscillatory ball mill (mixer mill MM301, Retsch GmbH and Co., Weinheim, Germany)	25 mL Stainless steel	2 stainless steel balls (d = 12 mm) 1 g s	30 Hz	12 ± 3 °C	180 min, stop every 30 min to scrape and remix powder	[74]
		Ranitidine, form 2 (with traces of form 1)					35 °C	120 min, stop every 30 min to scrape and remix powder
		Ranitidine, form 2						240 min, stop every 30 min to scrape and remix powder
2P	Chlorhexidine dihydrochloride	2-step polymorphism produces ChxHC form 2 as a precursor of form 3	High-energy planetary mill (Pulverisette 7; Fritsch, Idar-Oberstein)	43 cm3 ZrO2	7 ZrO2 balls (d = 15 mm) 1 g	6.6 Hz	Room temperature	12 h (15 min milling periods with 5 min rests)	[140]
3P	Γ-sorbitol	A form sorbitol	High-energy planetary micro-mill (Pulverisette 7; Fritsch, Idar-Oberstein)	45 cm3 zirconium	7 zirconium balls (d = 15 mm) 1 g of sample	6.6 Hz	Room temperature	10 h	[34]
4P	Rivastigmine (RHT form 2)	RHT form I	Retsch planetary ball mill PM100	50 mL stainless steel	3 stainless steel balls (d = 20 mm) 1 g	6.6 Hz	Room temperature	3 h (stopping at 15 min, 30 min, 1 h and 2 h)	[141]
5P	o-Aminobenzoic acid (mixture of FII and FIII forms)	FIII form	Oscillatory ball mill (Mixer mill MM400, Retsch GmbH and Co., Germany)	25 mL stainless steel	One stainless steel ball (d = 15 mm) 0.5 g 30 μL of solvent	25 Hz	Room temperature	2.5 h (30 min milling periods with 15 min pauses) Solvent: valeric acid (FIV and FIII)	[54]
		FII form
	m-Aminobenzoic acid (FIII form)	FIV form
		FIV and FIII
	Carbamazepine	FIV form
	p-aminobenzoic acid	β-PABA			1 stainless steel ball (d = 15 mm) 0.5 g 30 μL of solvent		Cryogenic temperature (immersed in liquid N2 for 5 min prior to miling every 7.5 min)	2.5 h (7.5 min milling and 2.5 min pauses in liquid nitrogen) Solvent: valeric acid, 10% acetamide or ethanol. (FI)
	o-Aminobenzoic acid (mixture of FII and FIII forms)	FI form (FII converts to FIII and subsequently FIII converts to FI.)
		FI form
6P	Dexamethasone	DEX form A and B	High-energy planetary mill (Pulverisette 7, Fritsch, Idar-Oberstein)	43 cm3 ZrO2	7 ZrO2 balls (d = 15 mm) 1.1 g	6.6 Hz	Room temperature	12 h (15 min milling periods, with 5 min rests)	[27]
7P	Sofosbuvir (anhydrous form 1)	Form A or B	Vibrational ball mill (MM400, RETSCH)	5 mL stainless steel	2 stainless steel balls (d = 5 mm) 50 mg 10 μL of Solvent	25 Hz	Room temperature	30 min Solvent: water or methanol	[79]
		Form A						30 min Solvent: anisole, n-butyl acetate, or ethyl acetate
		Form A (form 1 changes to form V)						30 min Solvent: anisole
		Form A						60 min, solvent: tetrahydrofuran
		Form A (form 1 changes into form B and then forms A)						20 min, solvent: butyl acetate or ethyl acetate
8P	Sulindac (form II)	Form II and form I	High-energy planetary mill (Pulverisette 7eFritsch)	43 cm3 ZrO2	7 ZrO2 balls (d = 15 mm) 1 g	6.6 Hz	Room temperature	5 min	[69]
		Form I						600 min (10 min milling, with 5 min pauses)
		Mixture of form II and form I						20 min (10 min milling periods, with 5 min pauses)
9P	Γ-sorbitol	A form sorbitol	High-energy planetary mill (Pulverisette 7-Fritsch)	43 cm3 ZrO2	7 ZrO2 balls (d = 15 mm)	6.6 Hz	Room temperature (dry nitrogen atmosphere)	10 h	[75]
	Mannitol (β)	α Mannitol
	Mannitol (δ)	α Mannitol
10P	Famotidine (form B)	Form A (form B to A transformation ratio increased with milling time)	Oscillatory ball mill (Mixer Mill MM301, Retsch GmbH and Co., Germany)	25 mL stainless steel	2 stainless steel balls (d = 12 mm) 0.2 g	15 Hz	130 °C	10 min	[142]
							110 °C	20 min
							110 °C	30 min
11P	Gabapentin (GBP) form I	GBP form II	Oscillatory ball mill (Mixer Mill MM301, Retsch GmbH and Co., Germany)	25 mL stainless steel	2 stainless steel balls (d = 15 mm) 0.2 g of sample	20 Hz	Room temperature	120 min	[76]
	GBP form II	GBP form III						105 min
		GBP form IV						120 min
	GBP form III	GBP form II						15 min
		GBP form III (produced by the coexistence of form I and II after 15 min milling)						60 min
		GBP form IV						105 min
	GBP form IV	GBP form II						2 min
		GBP form III						30 min
		GBP form IV						105 min
12P	Ciprofloxacin salicylate (monohydrate)	Form I (after 4 min of neat grinding) From 2 (after 9.5 min of neat grinding)	Fritsch planetary micro mill, model Pulverisette 7	12 mL agate	10 agate balls (d = 5 mm) 0.1 g 60 μL of solvent	8.3 Hz	NR	50 min, solvent: water, and the use of water/organic solvents decreases the time of existence for form I	[143]
	Ciprofloxacin salicylate (3.67 hydrate)	Form II (after 17 min of neat grinding)
	Anhydrous ciprofloxacin salicylate	From I
13P	γ-sorbitol	Form α (complete transformation)	High-energy planetary mill (Pulveri- sette, 7-Fritsch)	43 cm3 ZrO2	7 ZrO2 balls (d = 15 mm)	6.6 Hz	Room temperature	180 min (10 min milling periods, with 5 min rests)	[144]
14P	Ethenzamide: ethylmalonic acid (Co-crystal)	Form l (SDG with n-hexane) Form ll (after neat grinding or SDG with toluene or cyclohexane)	Oscillatory ball mill (Mixer Mill MM301, Retsch GmbH and Co., Germany)	10 mL stainless steel	1 stainless steel ball (d = 7 mm) 0.1 g of EA and 0.0799 g of EMA (1:1 molar ratio) 0.05 mL of solvent	20 Hz	Room temperature	15 min, solvent: toluene, cyclohexane, or n-hexane	[145]
15P	Caffeine: glutaric acid (co-crystal)	Form l (after neat grinding and SDG with n-hexane, cyclohexane or heptane)	Oscillatory ball mill (Mixer Mill, Retsch GmbH and Co., Germany)	Stainless steel (volume NR)	2 stainless stell balls (d = NR) 0.75 g (1:1 molar ratio)	30 Hz	Room temperature	60 min Solvent: n-hexane, cyclohexane, or heptane	[146]

NR: not reported; SDG: solvent drop grinding.